Streusel Coffee Cake

Directions

For the Cinnamon Filling:

1. In a small bowl, whisk together the brown sugar, flour, and cinnamon. Set aside.

For the Streusel Topping:

1. In a bowl, whisk together the flour, brown sugar, cinnamon, and salt.
2. Add the diced butter. Use your clean fingers or a fork to press and crumble the butter into the dry mixture until it becomes crumbly and resembles wet sand.
3. For larger crumbles, squeeze a handful of the mixture together and break apart into large pieces. Set aside.

For the Cake:

1. Preheat the oven to 350°F (175°C). Lightly grease an 8x8-inch square baking pan and line it with parchment paper.
2. In a bowl, whisk together flour, baking powder, and salt.
3. In a large mixing bowl or the bowl of a stand mixer fitted with the paddle attachment, beat the butter and both sugars on medium speed until light and fluffy, about 3 minutes.
4. Add the eggs one at a time, beating well after each addition. Scrape down the bowl.
5. Add the sour cream and vanilla extract, then mix on low speed until combined. Scrape down the bowl again.
6. Add the dry mixture to the wet mixture and beat on low speed until just combined. Use a spatula to scrape the bowl down and mix in any stray bits.
7. Spread half of the cake batter into the prepared pan and smooth it out.
8. Sprinkle the Cinnamon Filling evenly on top.
9. Dollop the remaining batter over the cinnamon filling, then gently spread it into an even layer, moving from the center outward.
10. Sprinkle the Streusel Topping over the cake, starting at the edges and working toward the center. (This ensures the cake rises evenly.)
11. Bake for 55 minutes, or until a toothpick inserted in the center comes out clean.
12. Allow the cake to cool in the pan for 30 minutes before serving.

For the Glaze (Optional):

1. If making the glaze, whisk together the powdered sugar, milk, and vanilla in a small bowl until smooth.
2. Drizzle over the coffee cake before or after slicing.