Preheat the oven to 425˚F. Put buttermilk, eggs, melted butter, and vanilla in a bowl. Beat until combined.
Add the flour, granulated sugar, baking powder, baking soda, and salt to the wet ingredients. Stir until just combined.
Fold in the blueberries.
Fill 12 lined muffin tin cups. Sprinkle with coarse sugar.
Bake at 425˚F for 5 minutes. Then, leaving the pan in the oven, turn it down to 350˚F and continue baking the muffins for 16-18 minutes or until a toothpick inserted in the center comes out clean.
Cool in pan for 10 minutes. Remove from pan and cool completely on wire rack.
Video
Notes
Store muffins in an airtight container at room temperature for 1-2 days, in the fridge for up to a week, or in the freezer for 2-3 months.