Prep the pan: Heat your oven to 400°F (200°C). Line a 12-cup muffin tin with paper liners or lightly grease the cups.
Mix dry ingredients: In a large bowl, whisk together the flour, baking powder, baking soda, and salt.
Whisk in the 2/3 cup sugar to evenly distribute.
Whisk the wet ingredients: In a separate bowl or large measuring cup, whisk the eggs, buttermilk, melted butter, oil, vanilla, and lemon zest until smooth.
Combine gently: Pour the wet mixture into the dry ingredients. Use a spatula to fold just until the flour is mostly moistened. The batter should be thick and a little lumpy. Do not overmix.
Prep the berries: Toss the blueberries with 1 tablespoon flour to help keep them from sinking.
Fold them into the batter with as few strokes as possible.
Fill the cups: Divide the batter evenly among the 12 muffin cups, filling them almost to the top for nicely domed muffins. Sprinkle with coarse sugar or the extra granulated sugar.
Bake hot, then finish: Bake at 400°F (200°C) for 8 minutes to boost the rise. Without opening the door, reduce the oven to 350°F (175°C) and bake 10–12 more minutes, or until the tops are golden and a toothpick comes out with moist crumbs.
Cool slightly: Let the muffins cool in the pan for 5 minutes, then transfer to a rack.
Serve warm or at room temperature.