Double Dose Cinnamon Coffee Cake

I call this double dose because it has a sweet cinnamon sugar filling and a crisp stresuel topping - two doses of cinnamon and brown sugar. This makes the cake extra decadent and delicious. It is a firmer cake, not as moist, but it needs to be to hold up well. Enjoy for breakfast, dessert, or an afternoon snack with coffee or tea. It is especially good warm. 

Double Dose Cinnamon Coffee Cake
TOPPING
1 cup all-purpose (plain) flour
1 cup packed light brown sugar
2 teaspoons ground cinnamon
1/2 cup butter or hard margarine, melted
FILLING
1/3 cup packed light brown sugar
1 teaspoon ground cinnamon
CAKE
3/4 cup butter or hard margarine, softened
1/3 cup packed brown sugar
1/2 cup granulated (white) sugar
2 large eggs
1 Tablespoon oil
2 teaspoons vanilla extract
2 cups all-purpose (plain) flour
1 teaspoon baking powder
1/4 teaspoon baking soda
2/3 cup buttermilk

TOPPING: Mix all together until well combined.
FILLING: Mix together.
CAKE: Preheat oven to 325◦F. Grease or line a 9x13-inch rectangular baking pan. 
Cream the butter and sugars together until light and fluffy. Beat in the eggs, one at a time, then the oil and vanilla. Stir in 1 cup flour, the baking powder and soda. Stir in 1/3 cup buttermilk. Stir in the remaining one cup flour than the remaining 1/3 cup buttermilk.

Spread half the batter into prepared pan. Sprinkle evenly with filling. Top with remaining batter, then topping. Bake for about 45-50 minutes until a toothpick inserted in the center comes out clean.