Step 1: Preheat oven to 350°F.
Coat a 9" x 11" baking pan with cooking spray and line with parchment paper. Spread the raspberries and blueberries around the bottom of the pan.
Combine the flour, salt, sugar, baking powder in a mixing bowl and blend well.
Combine the buttermilk, sweetened condensed milk, eggs, vanilla in a separate bowl and blend well. Add the wet mixture to the dry mixture and blend. Drizzle the melted butter on top of the batter.
Pour batter over the berries. Bake for 25 or 30 minutes or until a wooden pick inserted in the center comes out clean. Allow to cool on a rack for about 30 minutes before serving.
Step 6: TIP: Cake will keep a few days when covered well and refrigerated.