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 smooth and fully incorporated.
04 - Pour the wet ingredients into the dry ingredients. Gently fold together with a spatula just until combined. The batter should remain slightly lumpy—do not overmix.
05 - Toss blueberries with 1 tablespoon flour in a small bowl to coat. Gently fold the coated berries into the batter until evenly distributed.
06 - Divide batter evenly among the 12 muffin cups, filling each about three-quarters full. Sprinkle coarse sugar over the tops if using.
07 - Bake for 18 to 22 minutes, or until muffins are golden brown and a toothpick inserted into the center comes out clean.
08 - Let muffins cool in the tin for 5 minutes, then transfer to a wire rack to cool completely.