Step 1

Make Crust: Preheat oven to 375°F. Line a square 9-inch metal baking pan with parchment paper. Combine butter, sugar, and egg in a bowl with a spoon until well incorporated. Add flour, baking powder, and salt. Stir until no dry pockets remain. Sprinkle dough in prepared pan and press to make an even layer. Bake until lightly browned across surface, 12-15 minutes. Set aside to cool.

Step 2

Make Filling: Lower oven temperature to 350°F. In a stand mixer, beat together cream cheese and powdered sugar until well combined, about 2 minutes. Scrape down sides of bowl; add eggs, vanilla, and flour. Beat on low until combined. Increase speed and beat on medium-high until lightened and airy, about 3 minutes.

Step 3

Pour cream cheese mixture evenly over crust. Stir lemon curd to make sure it's loosened and dollop curd across surface of cream cheese mixture. Use a butter knife to make swirls in the lemon curd and cream cheese. Bake until evenly browned, rotating the baking pan halfway through baking, about 50 minutes. Allow to cool completely before removing from pan and slicing.