Blueberry Sour Cream Coffee Cake

### Instructions:

#### 1. **Preheat the Oven and Prepare the Pan**
Start by preheating your oven to 350°F (175°C). Grease a 9-inch round or square baking pan, or line it with parchment paper for easy removal of the cake once it’s done baking.

#### 2. **Make the Streusel Topping**
In a small bowl, combine the flour, brown sugar, and cinnamon. Add the cold butter pieces and, using a pastry cutter or your fingers, work the butter into the dry ingredients until the mixture resembles coarse crumbs. Set aside.

#### 3. **Prepare the Cake Batter**
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. In a separate large bowl, beat the softened butter and granulated sugar together until light and fluffy, about 2-3 minutes. Add the eggs, one at a time, beating well after each addition, and then stir in the vanilla extract.

Alternate adding the dry ingredients and the sour cream to the butter mixture, starting and ending with the dry ingredients. Mix until just combined; be careful not to overmix, as this can make the cake dense.

#### 4. **Fold in the Blueberries**
Gently fold the blueberries into the batter with a spatula, being careful not to crush them (especially if you’re using frozen berries, as they can break apart more easily).

#### 5. **Assemble the Cake**
Pour the batter into your prepared baking pan and spread it out evenly. Sprinkle the streusel topping over the batter, making sure to cover the entire surface.

#### 6. **Bake the Cake**
Place the pan in the preheated oven and bake for 45-55 minutes, or until a toothpick inserted into the center of the cake comes out clean. The top should be golden brown and slightly firm to the touch.

#### 7. **Cool and Serve**
Allow the cake to cool in the pan for 10-15 minutes before transferring it to a wire rack to cool completely. Once cooled, slice and serve. It’s perfect on its own or with a light dusting of powdered sugar. You can also enjoy it with a cup of coffee or tea for a delightful treat!

### Tips for Success:
– **Fresh vs. Frozen Blueberries**: Fresh blueberries work beautifully in this recipe, but if you’re using frozen, there’s no need to thaw them beforehand. Just toss them in a bit of flour to help prevent them from sinking to the bottom of the cake.
– **Make-Ahead**: This cake can be made ahead and stored in an airtight container at room temperature for up to 3 days. You can also freeze it for up to 3 months—just be sure to wrap it tightly in plastic wrap and foil.
– **Sour Cream Substitute**: If you don’t have sour cream, you can use plain Greek yogurt for a similar tang and creaminess.

### Why This Cake Is a Winner:
– **Tender Texture**: The combination of sour cream and butter gives the cake a moist and tender crumb that is perfect for a coffee cake.
– **Flavors that Pop**: The sweet, tart blueberries are the star of the show, complemented by the richness of the sour cream and the crunchy streusel topping.
– **Versatile**: While this cake is delicious on its own, you can also add a drizzle of glaze or a sprinkle of lemon zest for an added touch of flavor.

This Blueberry Sour Cream Coffee Cake is truly a showstopper that will become a favorite in your baking repertoire. Whether you’re serving it to guests or enjoying a quiet morning with a warm slice, it’s sure to satisfy. Happy baking!