Preheat the oven to 350 F and line an 8x8 inch pan with parchment paper. Stir together the flour, sugar, melted butter and salt until a soft dough forms, then press it evenly into the pan.
Bake the crust for 15-17 minutes until lightly golden at the edges.
While the crust bakes, add the cottage cheese, eggs, sugar, lemon juice, lemon zest and flour to a blender. Blend for 1-2 minutes until the filling is completely smooth.
Pour the filling over the warm crust.
Bake for 22-26 minutes until the filling is set with just a slight jiggle in the very center.
Cool to room temperature, then chill in the fridge for at least 2 hours. The cottage cheese makes the filling extra creamy, like a cross between lemon bars and custard.
Dust with powdered sugar and cut into squares.