Mix the butter with sugar and vanilla sugar until frothy. Gradually stir in the eggs. Mix the flour with baking powder, lemon zest and almonds and stir in alternately with the milk.
Peel, core and dice the apples and immediately fold into the batter.
Line a muffin tin with paper cases and fill in the batter (approx. 2 tablespoon per mold). Bake at 175 ° C for about 25 minutes.