1. Preheat oven to 350
degrees. Brush an 8-inch square baking dish with melted
butter. (This step is important because it will make it
easy for you to remove the parchment paper later.) Line
bottom with parchment paper, leaving a 2-inch overhang
on two sides.
2. To make the crust: Whisk almond flour/ground
nuts with graham-cracker crumbs, sugar, and zest. Mix in
butter. Press mixture into bottom and 1 inch up sides of
prepared pan. Bake until lightly browned, 8 to 12
minutes. Cool crust, 30 minutes.
3. To make the filling: In a large bowl, whisk
together egg yolks and condensed milk. Add lime juice
and lemon juice; whisk until smooth. Pour filling into
cooled crust; carefully spread to edges.
4. Bake until set, about 15 minutes. Cool in pan on
rack; then chill at least 1 hour before serving. Using
parchment paper overhang, lift out of pan, and transfer
to a cutting board. With a serrated knife, cut into 16
squares, wiping knife with a damp kitchen towel between