Use a whisk to beat the eggs;
Add the sugar and beat well;
Sift in the flour, add a pinch of salt and the lemon zest; stir until perfectly incorporated without any lumps;
Gradually pour in the milk and beat just until it’s well combined;
Line a 9-inch springform pan with parchment paper;
Peel and coarsely dice the apples;
Pour the batter into the baking pan along with the diced apples; the batter is quite liquid, so the apple pieces will sink to the bottom, but don’t worry; it is ok. The texture will change when baked;
Pre-heat the static oven to 350°F (180°C) and bake for about 35 minutes;
After 35 minutes, quickly open the oven and evenly sprinkle the cake with sugar; bake for another 5 minutes in the oven;
Let the cake cool down in the oven with the door slightly open;
It may flatten when you take it out of the oven, but it is ok. The edges should be crispy and lightly browned; that’s the tastiest part of the cake.