Preheat the oven to 400°F / 205°C. Grease and line an 8in / 20cm round cake pan. Whisk 180g of cake flour, 2 teaspoons of baking powder, and ¼ teaspoon of salt.
Beat 115g of softened unsalted butter, 200g of sugar, and the zest of 1 lemon for 3-5 minutes, until fluffy.
Separate 3 large eggs. Beat the yolks into the butter for 1 minute. Mix in 225g of whole-milk ricotta, 1½ teaspoons of vanilla paste and the flour mixture just until combined.
Beat the whites for 1-2 minutes, until frothy, without forming peaks. Beat into the batter until smooth.
Spread into the pan. Bake for 20-25 minutes, until deep golden. Cover loosely with foil and bake for 8-10 minutes more, until the center springs back.
Cool in the pan for 10 minutes, then turn onto a rack. Whisk 30g of lemon juice, 45g of coarse sparkling sugar, and 55g of icing sugar. Drizzle over the cake and let set for 30 minutes.
