
This lemon blueberry muffin recipe makes eight large big-topped muffins, ten standard muffins or 20 to 22 mini muffins (see note below about baking time for mini muffins). Fresh or frozen blueberries can be used. When using frozen, do not thaw them before adding to the batter.
Heat oven to 400 degrees Fahrenheit (204° C). For big-topped muffins, line 8 standard-size muffin cups with paper liners. For standard-size muffins line 10 muffin cups.
Use a microplane or citrus zester to remove the zest from a lemon. Add the zest (about 1 tablespoon) to a small bowl with the sugar. Rub the zest into the sugar until the sugar is perfumed by the lemon.
Whisk the flour, lemon 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). Measure 2 tablespoons of freshly squeezed lemon juice and then add it along with the vanilla. Whisk until well blended.
Add the 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.
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. (As another option, If you have another lemon, add a small, thin slice of lemon to the top of each muffin and sprinkle the sugar on top of the lemon slice.)
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.
To store, place cooled muffins in a plastic bag, seal, and store at room temperature for 2 to 3 days. To freeze, wrap them tightly in aluminum foil or place them in freezer bags. Freeze for up to 3 months.