Preheat oven to 350°.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients (flour through salt) in a medium bowl. Add milk, fruit puree, and vanilla; stir well. Stir in nuts.
Spoon the batter into an 8-inch square baking pan coated with cooking spray. Combine the brown sugar, 2 tablespoons granulated sugar, and 2 tablespoons cocoa; sprinkle over batter. Combine boiling water and coffee, stirring to dissolve. Pour coffee mixture over batter. (Do not stir.) Bake at 350° for 50 minutes or until cake springs back when touched lightly in center. Serve warm.