1. Preheat the oven to 230C/450°F.
2. On a baking sheet, covered with parchment paper, place the almonds. Bake and color the sliced almonds for 4 minutes. Reserve.
3. Lower the oven to 180C/350°F.
4. In a large bowl, with an electric whisk, whisk the sugar and butter until they are frothy.
5. Add the eggs one by one and mix after each addition.
6. Add the flour, half of the almonds, and the baking powder, mix gently. Reserve a few almonds for the top of the cake.
7. Add the diced apples. Mix.
8. Grease and flour a cake pan. Pour in the cake batter. Sprinkle the remaining almonds on top of the batter.
9. Bake for 35 minutes.
10. Pierce the center with the tip of a knife. If the knife comes out clean, remove the cake.
11. Place the cake on a rack and let it cool for 5 minutes before unmolding. Serve warm or cold