Preheat your oven to 400°F (200°C) before you start peeling and slicing the apples.

Line a round baking pan (about 8 inches/20 cm) with parchment paper, making sure it covers the bottom and sides. Add the butter in pieces and place the pan in the oven for 10 minutes, until the butter melts.

Wash, dry, and peel the apples, then slice them. As you slice, drizzle them with a little lemon juice to prevent browning.

Remove the pan with the melted butter from the oven. Arrange a layer of apple slices in a circular pattern, making sure there are no gaps. Sprinkle 1/3 of the sugar and half the cinnamon over the apples.

Repeat with a second layer of apples, then sprinkle the remaining sugar and cinnamon on top.

While the apples are baking, prepare the cake batter.

In a large bowl, whisk the eggs until light and fluffy.

Gradually add the sugar, whisking continuously.

Bake on the middle rack at 400°F (200°C) for 20 minutes. Check doneness with a knife; if it doesn't come out clean, bake for 5 more minutes.