Add all ingredients except for the pickle relish into the bowl of a food processor. Process until smooth, then taste and adjust the seasoning as necessary.
Pour the dressing into a bowl and stir in the pickle relish. Add up to 1 tablespoon more if desired.
Serve with your favorite salad and enjoy!
Notes
You can use your favorite ketchup, but I recommend using a natural ketchup that's low in sugar and doesn't contain artificial ingredients. I used just enough ketchup in this dressing to give it tomato flavor without making it too sweet.
If you like a spicier dressing, substitute the ketchup with chili sauce or add more horseradish.
Worcestershire sauce may be substituted with soy sauce, or make it gluten-free by using gluten-free soy sauce, tamari or coconut aminos.