Creating the Irresistible Blueberry Sour Cream Coffee Cake is simple and fun. Follow these easy steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan.
2. Combine Dry Ingredients: In a large bowl, whisk together the all-purpose flour, granulated sugar, brown sugar, baking powder, baking soda, salt, and cinnamon.
3. Blend Wet Ingredients: In another bowl, cream together the softened butter and sour cream until smooth. Beat in the eggs one at a time, followed by the vanilla extract.
4. Mix Together: Gradually combine the wet mixture into the dry ingredients. Stir until just combined; do not overmix.
5. Toss Blueberries: In a small bowl, toss the fresh blueberries with ½ cup of additional flour to coat them. This helps prevent them from sinking in the batter.
6. Fold in Blueberries: Gently fold the blueberries into the batter, being careful not to break them.
7. Pour Batter: Pour the batter into the prepared baking pan and smooth the top with a spatula.
8. Add Topping: If desired, sprinkle chopped nuts over the batter for added crunch.
9. Bake: Place the pan in the preheated oven and bake for 45-50 minutes, or until a toothpick inserted into the center comes out clean.
10. Cool Completely: Once baked, remove the cake from the oven and let it cool in the pan for 10-15 minutes. Then transfer it to a wire rack to cool completely.

By following these straightforward instructions, you’ll create a coffee cake that is wonderfully moist and bursting with flavor.