Mix ingredients necessary listed on the back of the cake mix to make batter. Preheat to necessary tempertaure (listed on back too).
Spray inside of 2 8" round cake pans. Pour half into one and half into the other. Bake for 28-32 minutes or until middle springs back when touched gently.
Put pans on top of a cooling rack until completely cooled. Carefully put a dinner plate on the top of the pan and flip over, it should slide out.
Use a sharp knife to cut it in half. Put a layer of frosting on one flat side of half of the cake. Pick up the other half and flip it over so that piece has the flat side facing down and on to the layer of frosting.
This will make 2 half birthday cakes made this way. frost the top and enjoy.