We have seen a recipe that added cinnamon to the batter and doubled the topping recipe. We tried it, but didn't care for it. Absolutely nothing beats this original recipe from the Bisquick box.
Cake
Topping
Cake
Topping
* Vanilla extract is not in the original recipe, but I think it makes a lot of difference. I always add it.
If using a 9 inch pie pan, it should be 1 1/2 to 2 inches deep.
1/2 cup chopped walnuts or pecans may be added to the Topping, if desired.
1/2 to 1 cup blueberries may be added to the batter, if desired.