Preheat the oven to 350?F (175?C). In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt. Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Gently fold in the mixed berries, banana slices, and diced apple into the batter.

Pour the batter into a greased cake pan and smooth the top.

Bake in the preheated oven for 30 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool for a few minutes before removing it from the pan. Serve with whipped cream on top.