Key Lime Bars have a buttery, flakey crust and a luscious key lime filling topped with powdered sugar.  They’re an easy dessert that always gets rave reviews!

key lime bars stacked up on a white serving board with powdered sugar

*This recipe was originally published in August 2013.  The photos and text have been updated and step by step photos have been added.

Sometimes the best recipes come to be by accident.  These Key Lime Bars were supposed to be lemon bars, but I realized last minute that I didn’t have any lemons.

A friend was visiting that loves lemon bars, and I thought this recipe would be just as good (if not better) with key limes.  I went ahead and baked this key lime version, and they were a huge success.

The fact that I often have fresh key lime juice stashed in my refrigerator or freezer speaks volumes about how much I love it.  I adore using it in my key lime smoothie, Greek yogurt dip and our favorite key lime pie.

It’s worth taking 5-10 minutes to juice a bag of key limes as it’s so much more fresh tasting than bottled!

key lime bars with powdered sugar and slice of key lime on top

Why you’ll love this key lime bar recipe

  • The tangy, sweet key lime filling is perfectly complimented by the buttery crust and dusting of powdered sugar.
  • This recipe takes minimal ingredients and prep!  
  • The crust is an easy shortbread crust that ‘s buttery, flaky and melts in your mouth.
  • This is an impressive dessert that everyone will love. 
  • Key lime juice may be substituted with any citrus that you have on hand.  

What’s the difference between key limes and limes?

Key limes are smaller and contain more seeds than regular limes.  It takes about 20 key limes to produce 1/2 cup or more of juice.

The main difference is the flavor.  Key limes are aromatic with a special flavor that’s tart and floral.

Recipe Ingredients

This recipe only requires 6 simple ingredients.

You’ll need:

  • Unsalted Butter.  Using unsalted butter allows you to control the sodium.  Allow the butter to soften at room temperature before preparing the crust.
  • All purpose flour.  The flour is used in the crust, and a small amount is used to thicken the filling as well.
  • Powdered sugar.  Powdered sugar provides the key lime bars with their trademark powdery white topping, and it’s also used to sweeten the crust.  Powdered sugar contains cornstarch, which gives the crust a soft, melt in your mouth texture.
  • Granulated sugar.  This is used to sweeten the key lime filling.
  • Fresh key limes.  You’ll need both zest and the juice for these key lime bars.  The key lime juice is the star of these bars, and fresh juice makes all the difference.  It’s got a bright, fresh flavor that bottled key lime juice just can’t provide.  If you can’t find fresh key limes, consider using lemons, regular limes or oranges.  
  • Eggs.  The eggs give the filling structure and a custard-like richness.

overhead shot of key lime bars on white serving board

How to make Key Lime Bars

This recipe is very easy to make following my simple instructions.

Place the butter and eggs on the counter to come to room temperature up to 30 minutes in advance

Cutting the butter into small pieces and placing the eggs in warm water will speed up the process.

Zest and juice the key limes 

Zest a few key limes for about a tablespoon of key lime zest, then juice the limes.  One bag of key limes will yield a minimum of 1/2 cup of juice.  Strain the juice, then stir the zest into the juice.  This may be done up to a few days in advance and it may also be frozen. 

Save one key lime for garnish if desired.

Preheat the oven

When you’re ready to get started, preheat the oven to 350 degrees and line the baking dish with parchment paper or foil to prevent sticking.

Prepare the crust

process collage for key lime bar crust

  • Beat the softened butter and powdered sugar until fluffy, about 2 minutes.  Beat in the flour and salt and mix just until combined.
  • Place the dough into the prepared pan and spread evenly with an offset spatula.
  • Bake the crust for 20-25 minutes or until lightly golden.  The crust will smell like shortbread!
  • Allow the crust to cool while you prepare the filling.

Prepare the key lime filling

It’s very important to combine the ingredients in the order listed to prevent lumps of flour in the filling.

key lime bar filling process collage

  • In a medium bowl, whisk the granulated sugar and eggs until well incorporated.
  • Next, add the flour and whisk until smooth.
  • Add the lime juice and zest, and whisk until combined.

Bake the bars

key lime bar crust before and after baking

  • Pour the key lime filling over the crust and bake for 20-25 minutes or just until set.  
  • It’s completely normal for the top of the key lime bars to be white with air bubbles!  Don’t worry, the powdered sugar will hide that.

Cut and garnish the bars with powdered sugar

key lime bars before and after powdered sugar

  • Place the cooled bars on a cutting board and cut with a very sharp knife.  Wipe the knife clean in between slices.
  • Using a mini strainer, dust powdered sugar over the top of the bars.

How to store Key Lime Bars

It’s fine for the key lime bars to remain at room temperature the day they are made, but any leftovers should be stored in an air tight container in the refrigerator.  

close up of three key lime bars stacked up on serving board

Key lime bar recipe FAQ’s

Below are some of the most commonly asked questions regarding this recipe.

How do I know when my key lime bars are done?

The bars are done when the filling is completely set.  Move the pan gently back and forth — the filling should not “wiggle”.

Do not over bake as this will result in the filling cracking.

Why did the top of my bars turn white?

This is a result of the eggs rising to the surface.  This is normal, and the powdered sugar will hide it!

How do you cut key lime bars cleanly?

The most important thing is to make sure that the bars have cooled completely, and cut before dusting them with powdered sugar.

Use a very sharp knife, wiping the knife clean in between slices.

Recipe notes

  • This recipe is easily doubled and baked in a 9×13″ glass baking dish.  For best results, use a glass baking dish.
  • Bars should be cooled completely at room temperature.  Dust with powdered sugar just before serving.
  • Refrigerate leftover key lime bars in an air tight container in the refrigerator for up to 5 days.
  • (1) bag of key limes contains about 20 limes, which yields a minimum of 1/2 cup key lime juice.  
  • Zest and juice key limes, then add the zest to the juice.  This may be done up to 2 days in advance and may be frozen.
  • Can’t find key limes?  You can easily substitute the key lime juice with any type of citrus juice. Lemon, orange, blood orange or grapefruit are all great options.

front angled shot of stack of key lime bars

More key lime recipes you’ll love:

Key lime cheesecake bars

Key lime cupcakes by Baker By Nature

Key lime ice cream

Key lime pie

key lime bars stacked up on a white serving board with powdered sugar

Key Lime Bars

Servings: 9 bars
Prep Time: 15 mins
Cook Time: 50 mins
Total Time: 1 hr 5 mins
Key Lime Bars are an easy key lime bar recipe with a buttery, flakey crust topped with a sweet, tangy key lime filling and powdered sugar!
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Ingredients

For the crust:

  • 1/2 cup unsalted butter softened
  • 1/4 cup powdered sugar
  • 1 cup all purpose flour
  • 1/4 teaspoon salt

For the filling:

  • 3 large eggs
  • 1 cup granulated sugar
  • 3 tablespoons all purpose flour
  • 1 tablespoon lime zest
  • 1/2 cup key lime juice
  • 1/2 cup sifted powdered sugar for garnish

Instructions 

  • Preheat oven to 350 degrees. Line an 8x8" baking dish with parchment paper or foil.

Prepare the crust:

  • In a large bowl, beat the butter and 1/4 cup powdered sugar till light and fluffy, about 2-3 minutes. Add flour and salt, and beat on low speed until just incorporated.
  • Scrape the dough into the prepared pan and spread evenly with an offset spatula. Bake on the middle rack of the oven 20-25 minutes, or until lightly golden. Remove from the oven and cool on a wire rack while you prepare the filling.

Prepare the filling:

  • In a medium bowl, whisk the eggs and granulated sugar until well incorporated. Add the 3 tablespoons of flour and whisk until combined, then whisk in the lime juice and zest.
  • Pour the filling over the cooled crust, and bake 20-25 minutes longer, or until the filling has set. The filling will not "wiggle" when the pan is moved gently back and forth. Remove from heat and cool completely on a wire rack.
  • Once the key lime bars have cooled, cut into squares with a sharp knife, wiping the knife clean in between slices. Dust with powdered sugar, serve and enjoy!

Notes

  • This recipe is easily doubled and baked in a 9x13" glass baking dish.  For best results, use a glass baking dish.
  • Bars should be cooled completely at room temperature.  Dust with powdered sugar just before serving.
  • Refrigerate leftover key lime bars in an air tight container in the refrigerator for up to 5 days.
  • (1) bag of key limes contains about 20 limes, which yields a minimum of 1/2 cup key lime juice.  
  • Zest and juice key limes, then add the zest to the juice.  This may be done up to 2 days in advance and may be frozen.
  • Can't find key limes?  You can easily substitute the key lime juice with any type of citrus juice. Lemon, orange, blood orange or grapefruit are all great options.

Nutrition

Serving: 1g, Calories: 312kcal, Carbohydrates: 48g, Protein: 4g, Fat: 12g, Saturated Fat: 7g, Polyunsaturated Fat: 4g, Cholesterol: 89mg, Sodium: 85mg, Fiber: 1g, Sugar: 35g

Nutrition is estimated using a food database and is only intended to be used as a guideline for informational purposes.

Course: Sweets
Cuisine: American
Author: Marcie
Keyword: key lime bar recipe, key lime bars
All recipes and images © Flavor the Moments.
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