Step 1

Preheat oven to 350°F. Spray a 9-inch round or square pan with baking spray.

Step 2

In a large mixing bowl, mix together the flour, sugar, baking powder, and salt. Set aside.

Step 3

In a medium bowl, mix together the butter, oil, eggs, milk, and vanilla until combined.

Step 4

Add the wet ingredients to the dry ingredients. Stir just until most of the streaks of flour are incorporated.

Step 5

Fold in the mixed berries, being careful not to smash them. If using frozen mixed berries, do not defrost them before adding them to the batter. Transfer the cake batter to the prepared cake pan.

Step 6

Make the crumb topping by mixing the flour, sugar, and salt together in a medium bowl. Add the melted butter using a fork until evenly moistened and crumbly. Sprinkle evenly over the cake batter.

Step 7

Bake for 40-45 minutes, until done. Cool for at least 10-15 minutes before serving.