Cooking instructions: Preheat the oven to 350°F. Grate the lemon peel and juice the lemon. Whip the egg yolks together with the granulated sugar, then mix in the ricotta, the potato flour, and the lemon peel and juice, and mix with electric beaters until smooth. Beat the egg whites until stiff and gently fold into mixture. Line an 8”-round/2”-high cake pan with parchment paper, pour in the mixture, and bake for around 40 minutes. Remove the cake from the oven and let cool. Sprinkle with powdered sugar and serve.