Step 1

Whisk together 2 1/2 cups of the flour and the baking powder in a medium bowl until completely combined. Toss 1 1/2 cups of the blueberries with the remaining 2 tablespoons flour in a medium bowl until completely coated. Whisk together the buttermilk, sour cream, vanilla and salt in a large measuring cup until smooth.

Step 2

Arrange a rack in the center of the oven and preheat to 425 degrees F. Spray the top of a 12-cup muffin tin with nonstick spray and line with standard cupcake liners. (It's important to spray the top of the pan because the muffin tops will stick to the pan if you don't.)

Step 3

Beat the butter, granulated sugar and lemon zest with an electric mixer on medium-high speed until light and fluffy, occasionally scraping down the sides and bottom of the bowl, 3 to 4 minutes. Add the egg and yolks and continue beating until fully incorporated, about 2 minutes.

Step 4

With the mixer on low, add the dry ingredients in 3 additions, alternating with the wet ingredients in 2 additions, beginning and ending with the dry ingredients. Fold in the blueberries until evenly distributed (be careful not to overmix).

Step 5

Divide the batter evenly among the prepared muffin cups with a heaping 1/3 cup per muffin. Top the batter with the remaining 1/2 cup blueberries, gently pressing to adhere (you should have 4 to 5 berries per muffin). Sprinkle with the raw sugar.

Step 6

Bake the muffins, rotating the pan halfway through, until a tester inserted into the center comes out clean, 25 to 30 minutes. Transfer the pan to a wire rack and let the muffins cool in the pan for 5 minutes. Then remove the muffins onto the wire rack to cool completely.