Mix the granulated sugar and cinnamon together in a small bowl and set aside.

Preheat the oven to 350 degrees. Line baking sheets with parchment paper or silicone liners.

Whisk together the flour, baking soda, cinnamon, cream of tartar, and salt. Set aside.

In a large mixing bowl, beat the butter, granulated sugar, and brown sugar with an electric mixer on medium speed until light and fluffy. Add the eggs, one at a time, mixing well after each addition. Mix in the vanilla.

Reduce the mixer speed to low. Gradually add the flour mixture, mixing just until combined.

Using a tablespoon or 1/2" cookie scoop, scoop out the dough and roll into balls. Roll in the cinnamon-sugar, then place on the prepared baking sheets 2" apart. Bake for 8-10 minutes, or until lightly browned and set. Allow to cool on the pans for 10 minutes, then transfer cookies to a wire rack to cool completely.

In a medium bowl, beat the cream cheese, butter, and vanilla together with an electric mixer on medium speed until smooth. Gradually add the powdered sugar, and beat until thoroughly combined and smooth. Stir in the coconut.

Spread the frosting on the bottom half of the cookies. Top with the remaining cookies, and press together lightly so that the frosting spreads to the edges. Enjoy!