1 cup softened butter
1 1/2 cups white sugar
2 tsp vanilla extract
3 cups flour
1 tsp baking soda
2 tsp baking powder
2 tsp salt
2/3 cup yogurt
2/3 cup sour cream
1/4 cup vegetable oil
Beat the sugar and butter together until smooth, then beat in the yogurt, sour cream, oil and vanilla. Mix the dry ingredients together and then stir into the wet mixture. Spoon about 2/3 of the batter into a greased 9X13 inch cake pan. Sprinkle your choice of fillings as below, then dot the remaining batter on top of the filling. Finally, evenly sprinkle the streusel topping over everything. Bake at 350 degrees for about an hour, until nicely browned and a toothpick stuck in the center comes out clean. Allow to cool before cutting.
Streusel: ½ stick soft or melted butter, 1 ½ cups sugar, 1 cup flour. Mix together with fork or your hand, until it makes clumps. Sprinkle the clumps over the everything.
Sprinkle heavily with brown sugar, cinnamon and pecans.
Or: Sprinkle heavily with some sort of berry or cherry, fresh or frozen. If you use cherries, add a small amount of almond extract to the batter, in addition to the vanilla.
Or: Rhubarb, chop fresh or frozen rhubarb, sprinkle lightly with a couple tablespoons of sugar, then put over the batter.
This is especially good with fresh or frozen gooseberries.