Prep your pan and oven: Heat the oven to 400°F (200°C). Line a 12-cup muffin tin with paper liners or grease lightly.

Whisk the dry ingredients: In a large bowl, whisk 2 cups flour, sugar, baking powder, baking soda, and salt until well combined.

Combine wet ingredients: In a medium bowl, whisk melted butter, oil, buttermilk, yogurt, eggs, lemon zest, lemon juice, and vanilla until smooth.

Toss the blueberries: In a small bowl, toss blueberries with 1 tablespoon flour to coat. This helps keep them from sinking.

Make the batter: Pour the wet mixture into the dry ingredients. Stir gently with a spatula just until most streaks of flour are gone. The batter should be thick. Do not overmix.

Fold in blueberries: Add the floured blueberries and fold in gently to avoid smashing them.

Fill the muffin cups: Divide batter evenly among the 12 cups, filling them almost to the top. Sprinkle with coarse sugar if using for a little crunch.

Bake hot, then reduce: Place the pan in the oven and bake at 400°F for 5 minutes. Without opening the door, reduce heat to 350°F (175°C) and bake another 12–15 minutes, until the tops are golden and a toothpick comes out clean or with a few moist crumbs.

Cool: Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before glazing.

Mix the glaze: In a small bowl, whisk powdered sugar with 2 tablespoons lemon juice, lemon zest, and a pinch of salt. Add more lemon juice a few drops at a time until the glaze is thick but pourable.

Glaze and set: Spoon or drizzle the glaze over cooled muffins. Let it set for 10–15 minutes before serving.