For the strawberry sheet cake, first melt the butter and let it cool a little. Wash the strawberries, remove the stems and cut them in half lengthwise.
Cover a baking tray with baking paper. Preheat the oven to 180 °C.
Sift together the flour and baking powder. Beat butter, sugar and eggs until fluffy. Add vanilla sugar and continue beating well. Quickly fold in flour mixture.
Spread the batter on the baking sheet. Place strawberries on top, skin side down. Bake for about 25 minutes (test with chopsticks).
Let the strawberry sheet cake cool, remove the baking paper and cut the cake into pieces.
You can find the video for this recipe here.