Blueberry Sour Cream Coffee Cake

Preheat your oven to 350°F (175°C). Grease and flour a 9-inch round or square cake pan, or line it with parchment paper for easy removal.
Make the Cake Batter:

In a large mixing bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy, about 2-3 minutes.
Add the vanilla extract and eggs, one at a time, beating well after each addition.
In a separate bowl, whisk together the flour, baking soda, and baking powder.
Gradually add the dry ingredients to the wet ingredients, alternating with the sour cream. Start and end with the dry ingredients, mixing just until combined.
Gently fold in 1 cup of the fresh blueberries.
Prepare the Streusel Filling:

In a small bowl, combine the melted butter, brown sugar, and cinnamon. Stir until well mixed.
Assemble the Coffee Cake:

Pour half of the cake batter into the prepared pan and smooth the top. Sprinkle the streusel filling evenly over the batter.
Top the streusel layer with the remaining cake batter and spread it out gently. Sprinkle the remaining ½ cup of blueberries on top of the batter.
Bake:

Bake in the preheated oven for 50-60 minutes, or until a toothpick inserted into the center of the cake comes out clean or with just a few moist crumbs.
If the top is browning too quickly, tent the cake with foil and continue baking.
Cool and Serve:

Allow the cake to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely. Slice and serve warm or at room temperature.
Serving and Storage Tips: