Preheat oven to 350°F. Grease a 2-quart baking dish with nonstick spray or butter. In a bowl, mash raspberries with a fork or potato masher and set aside.
In a bowl combine flour, 2 tablespoons cocoa powder, baking powder, and salt.
In a large bowl, beat together melted butter, 3/4 cup brown sugar, and vanilla.
Stir in half the flour mixture, then all of the milk, then the remaining flour mixture, making sure to scrape the sides and bottom of the bowl and mixing until smooth.
Spread batter into the baking dish. Spoon raspberries over batter. Combine remaining brown sugar and cocoa powder and sprinkle evenly over the top.
Bake about 30 minutes or until wooden toothpick, inserted about 1/2 inch into cake portion, comes out clean. Let cool slightly, then serve warm.