Peel and core the apples, cut into cubes (5 - 8 mm) and drizzle with lemon juice.
Mix the butter and sugar until creamy. Mix in the eggs and poppy seeds. Mix the baking powder with the flour and stir into the mixture alternately with the milk. Add the lemon zest and vanilla sugar and finally mix in the apple cubes. Line a baking sheet with parchment paper and spread the dough on it.
Slide the tin on the middle rack into the oven and bake the cake for approx. 45 minutes at 175 ° C.
The dough is suitable for a sheet metal shape of 29 x 21 cm.