Preheat oven at 320oF Blends the butter, flour, baking powder, sugar, and lemon rind in a food processor until it resembles breadcrumbs.
After this, Keep the motor running and add the egg yolks. Process until combined.
Place the batter in a 9×9 inch square pan lined with parchment.
Now Bake for 20-25 minutes, or until it is firm to the touch.
Mix the sugar, egg yolk, sugar, vanilla, lemon rind, vanilla, and mascarpone in a bowl until smooth.
After this, Bake for 30-35 minutes, or until the top is golden and the middle is set. After this, Allow cooling in the refrigerator for at least three hours, or until set.