01 - Preheat oven to 400°F. Line a 12-cup muffin tin with paper liners or grease thoroughly with cooking spray.
02 - In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt until well blended.
03 - In a separate bowl, whisk eggs, oil or melted butter, yogurt or buttermilk, lemon zest, lemon juice, and vanilla extract until completely smooth.
04 - Pour wet ingredients into dry ingredients. Gently fold together just until combined—do not overmix as this will result in tough muffins.
05 - Toss blueberries with 1 tablespoon flour in a small bowl to prevent sinking. Gently fold coated berries into the batter using a spatula.
06 - Divide batter evenly among the 12 muffin cups, filling each about three-quarters full. Sprinkle tops with coarse sugar if using.
07 - Bake for 18 to 22 minutes until tops are golden brown and a toothpick inserted into the center of a muffin comes out clean.
08 - Let muffins cool in the tin for 5 minutes, then carefully transfer to a wire rack to cool completely before serving.