We will start by preheating the oven to 180ºC. Butter and sprinkle a mold about 22 cm in diameter with flour. Beat with a wire mixer butter and sugar until it has doubled in volume and has turned like a pale cream. Mix the lightly beaten egg yolks and the crumbled ricotta cheese.
Beat the whites until stiff until they form peaks. Add them carefully to the mixture. Add the yeast flour. To incorporate gently until you see everything well mixed. Pour a not too thick layer of the mixture into the bottom of the pan. Place some blackberries. Keep repeating this operation until the dough is finished, reserving blackberries for decoration.
Bake for 35 minutes approximately or until when punctured with a skewer it comes out clean. Leave it for about ten minutes and unmold to finish cooling on a rack.