Heat the oven to 175 C / 350 F. Grease a 9-inch round cake pan and line the base with parchment paper.

If your ricotta looks wet, spoon it into a fine-mesh sieve set over a bowl and let it drain for 15 minutes. Discard the liquid.

Peel and core the apples. Dice them into roughly 1 cm cubes and set aside.

In a large mixing bowl, whisk the eggs and sugar together until pale and slightly thickened, about 2 minutes by hand.

Add the drained ricotta, melted butter, vanilla extract, and lemon zest. Whisk until smooth and combined.

Sift the flour, baking powder, and salt directly into the bowl. Fold with a rubber spatula until just combined - stop as soon as no dry flour is visible. Do not overmix.

Fold in the diced apples until evenly distributed through the batter.

Pour the batter into the prepared pan and smooth the top with the spatula.

Bake on the center rack for 40 to 45 minutes, until the top is golden and a skewer inserted into the center comes out with moist crumbs but no wet batter.

Cool the cake in the pan on a wire rack for 20 minutes, then turn out and cool completely before slicing. Dust with powdered sugar just before serving if you like.