Ingredients:
2 cups all-purpose flour
1 cup granulated sugar
1/2 cup unsalted butter, at room temperature
2 teaspoons baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup sour cream
2 large eggs
1 teaspoon vanilla extract
For the streusel topping:
1/2 cup all-purpose flour
1/2 cup brown sugar
1/2 teaspoon cinnamon
1/4 cup unsalted butter, at room temperature
Instructions:
Preheat the oven to 350°F (175°C) and grease a 9×13 inch baking dish.
To make the streusel topping, combine the flour, brown sugar, and cinnamon in a small bowl. Cut in the butter with a pastry cutter or your fingers until the mixture is crumbly. Set aside.
In a large mixing bowl, cream the butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition.
Stir in the vanilla extract.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Add the dry ingredients to the wet ingredients in two or three parts, alternating with the sour cream, and mixing until just combined.
Pour half the batter into the prepared baking dish.
Sprinkle half the streusel topping over the batter.
Pour the remaining batter over the streusel layer.
Sprinkle the remaining streusel over the top of the second layer of batter.
Bake for 35-40 minutes, or until a toothpick inserted in the center comes out clean.
Allow the cake to cool for at least 10 minutes before serving.