• Preheat the oven to 350°F. Line a standard muffin pan with paper liners. Set aside.
• In a medium bowl, whisk together 2 cups of the flour with the baking powder, baking soda, and salt. Set aside.
• In the bowl of a stand mixer fitted with the paddle attachment or with an electric hand mixer, cream together ½ cup butter with the granulated sugar until light and fluffy, about 3 minutes, scraping down the sides of the bowl as needed.
• Add the eggs one at a time, beating well after each addition. Add the vanilla; beat to combine.
• Add half of the flour mixture; mix on low speed until just combined. Add all of the buttermilk; mix until just combined. Add the remaining flour mixture, mixing until just combined. Scrape the sides and bottom of the bowl to ensure the batter is well mixed.
• In a small bowl, toss the blueberries with the remaining 1 tablespoon of flour. Gently fold the blueberries into the batter with a rubber spatula.
• Divide the batter evenly among the lined muffin cups. Set pan aside.

Make the crumb topping:

• In a small bowl, mix together brown sugar, flour and cinnamon. Cut in butter until evenly distributed and crumbly in texture. Sprinkle topping over muffins.
• Bake for 22-27 minutes, or until a toothpick inserted into the center comes out clean.
• Let muffins cool slightly before removing from the pan. Place on a wire rack to cool completely.