Preheat the oven to 350°F (175°C). Grease and flour a cake pan.

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs one at a time, mixing 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, sliced banana, and diced peaches into the batter.

Pour the batter into the prepared cake pan and smooth the top.

Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.