Step 1

Preheat oven to 350°F. Butter bottom and sides of an 8-inch square baking dish. Line with parchment paper with 2-inch overhang.

Step 2

In a stand mixer with paddle attachment, mix butter, flour, and powdered sugar together on low speed until dough starts to form clumps.

Step 3

Flour your hands to press dough into bottom and ½-inch up sides of parchment lined baking dish.

Step 4

Bake in preheated oven until light golden brown, 20-22 minutes. Remove from oven and place on cooling rack.

Step 5

While crust bakes, beat eggs with an electric mixer on medium speed until light and foamy.

Step 6

Add sugar, flour, key lime juice, zest, baking powder, and salt. Mix until well combined. Pour key lime mixture over crust.

Step 7

Bake 22-25 minutes until edges are lightly golden and center is set.

Step 8

Cool in baking dish on rack. Then chill at least 1 hour before serving. (Can be made 2 days ahead. Keep refrigerated.)

Step 9

Use parchment paper overhang to remove from pan and cut into squares. Dust with powdered sugar and garnish with quartered lime wedges and additional zest, if desired.