Easy buttermilk fruit cake

Ingredients: (baking pan 24x24 cm)

3 eggs
1/2 cup granulated or bakers sugar
1 tablespoon vanilla sugar
pinch of salt
1/2 cup buttermilk
1/3 cup oil
1 1/2 cup all-purpose flour
1 1/2 teaspoon baking powder
500 g fruit
Crumble:
50 g unsalted butter at room temperature
80 g all-purpose flour (1/2 cup)
40 g powdered sugar (1/3 cup)