In a bowl beat 1 cup unsalted butter until light and creamy.
Add 2 egg yolks and mix well.
Add 1 cup sugar, beating a few minutes until almost incorporated.
Add 2 cups all-purpose flour, 1 teaspoon baking powder and ¼ teaspoon salt. Incorporate with a wooden spoon or spatula; it will be a tad sticky.
Divide in two and wrap in plastic. Freeze until hard but not rock solid, about 45 minutes.
Preheat oven to 375ºF (190ºC).
Line an 8-inch square pan with parchment paper. See Notes below.
Using a wide holed grater, grate one of the dough pieces, letting it cover the bottom of the pan. Press lightly to avoid holes or parts with no dough.
Cover the bottom dough with 11 ounces quince paste or jam. If it’s too stiff, soften it with a few tablespoons orange juice or water. Be careful not to tear the dough. I put the paste in tablespoons and then spread it with the back of a spoon or offset spatula.
Grate the rest of the cold dough, letting it fall as evenly as possible. Press very lightly if you want, but not much.
Bake for 15 minutes, turn the oven down to 350ºF / 180ºC and bake another 30 minutes, or until it’s golden, dry and it looks crunchy.
Let cool on wire rack, but if some parts of paste or jam are stuck to the sides, unstuck them while still hot with a non-serrated knife.