Heat oven to 400 degrees F. Line muffin tins with paper liners. Fill the remaining cups with 1 to 2 tablespoons of water to help the muffins bake evenly.

Make Batter

Whisk the flour, sugar, baking powder, and salt in a large bowl.

Add oil to a measuring jug that holds at least 1 cup. Add the egg then fill the jug to the 1-cup line with milk (1/3 to 1/2 cup milk). Add vanilla and whisk to combine.

Add milk mixture to the bowl with dry ingredients then use a fork to combine. Do not over mix. (The muffin batter will be quite thick — see note below for more details). Fold in the blueberries.

Bake Muffins

Divide the batter between muffin cups. (If making big-topped muffins, the batter will come to the tops of the paper liners). Sprinkle a little sugar on top of each muffin.

Bake muffins 15 to 20 minutes or until tops are no longer wet and a toothpick inserted into the middle of a muffin comes out with crumbs, not wet batter. Transfer to a cooling rack.

https://www.inspiredtaste.net/18982/our-favorite-easy-blueberry-muffin-recipe/