Preheat the oven to 350 degrees. Spray a 9-inch cake pan with cooking spray.
In a mixing bowl, whisk together the flour, cocoa powder, baking powder and soda, and salt.
In an electric mixer, preferably fitted with a paddle attachment, beat the butter and sugar together until light and fluffy, about 3 minutes. Add the eggs, one at a time, beating well after each addition. Turn the mixer to low, beat in half the flour mixture, the sour cream, and finally the rest of the flour. Using a spatula, stir in the melted chocolate chips, making sure all ingredients are fully combined. Pour the batter into the prepared baking pan and bake for 45 minutes or until a toothpick inserted into the center comes out clean. Let cool in the pan for 10 minutes then transfer to a wire rack to finish cooling completely.
Frosting
In an electric mixer, preferably fitted with a paddle attachment, beat the cream cheese and SunButter together until creamy. Add the powdered sugar, 1 cup at a time, and beat until the frosting reaches a spreading consistency. Beat in the vanilla. Refrigerate until ready to use.
To assemble, cut the cake in half horizontally. Place the bottom layer on a cake stand or platter. Spread some of the frosting on top, place the top layer on and frost the sides and top.