01 - Preheat oven to 400°F. Line a 12-cup muffin tin with paper liners or grease cups thoroughly with cooking spray.
02 - In a large mixing bowl, whisk together flour, sugar, baking powder, baking soda, and salt until evenly distributed.
03 - In a separate bowl, whisk eggs, oil or melted butter, yogurt or buttermilk, lemon zest, lemon juice, and vanilla extract until mixture is smooth and creamy.
04 - Pour wet ingredients into dry ingredients. Fold gently with a spatula just until combined; some small lumps should remain. Do not overmix as this creates tough muffins.
05 - Toss blueberries with 1 tablespoon flour in a small bowl to coat evenly. This prevents berries from sinking during baking.
06 - Gently fold floured blueberries into the batter using a spatula, taking care not to crush the fruit.
07 - Divide batter evenly among the 12 muffin cups, filling each about three-quarters full. Sprinkle tops with coarse sugar if using.
08 - Bake for 18 to 22 minutes, rotating pan halfway through, until tops are golden brown and a toothpick inserted into the center of a muffin comes out clean.
09 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely before serving.