Preheat the oven to 350°F (175°C). Grease and flour a 9x9-inch baking pan.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.
In a separate bowl, cream the softened butter with the granulated sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
Gradually mix in the dry ingredients alternately with the sour cream into the wet ingredients until well combined.
In a small bowl, combine the cinnamon and sugar for the swirl. In another bowl, prepare the streusel topping by mixing the flour, brown sugar, and cinnamon. Cut in the cold cubed butter until crumbly.
Pour half of the batter into the prepared baking pan. Sprinkle the cinnamon-sugar swirl mixture over the batter. Top with the remaining batter.
Sprinkle the streusel topping evenly over the top of the batter.
Bake in the preheated oven for 40-45 minutes or until a toothpick inserted into the center comes out clean.
Allow the coffee cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely. Slice and serve, enjoy!
Notes
Store leftovers in an airtight container at room temperature for up to 3 days or refrigerate for up to 1 week.For longer storage, wrap individual slices tightly with plastic wrap and freeze for up to 3 months. Thaw overnight at room temperature or gently warm in the microwave before serving.This coffee cake is perfect for breakfast, brunch, or a sweet treat with your afternoon coffee.