Preheat oven to 325°F. Line an 8-inch pan with parchment paper.

Combine flour, sugar, salt, and zest. Add melted butter. Press into pan.

Blind-bake crust for 15 minutes.

Whisk eggs, sugar, baking powder, juice, and remaining flour. Pour over crust.

Bake until set, about 25 minutes. Cool and refrigerate 2 hours.

Dust with confectioners’ sugar and cut into squares.