In a medium bowl, stir together the flour, sugar, baking powder, salt, and lemon zest. In a small bowl, stir together the milk, melted butter, vanilla extract, and the egg. Pour the wet ingredients into the dry.
Stir together for just a couple of turns. While there are still pockets of dry flour in the mixture, toss in your berries. Continue to stir together until no dry pockets remain, but do not over-mix.
Cover, and let the batter rest on your counter for 30 minutes. This will help everything come together before baking, and it also helps to ensure you get high-domed muffins.
Preheat your oven to 400 degrees. Spray your baking pan with baking spray- you want the spray to coat the top of the pan mostly to prevent overhang from sticking. Line with paper cups.
Once your batter has rested for a full 30 minutes, scoop evenly into your prepared pan. The muffin cups should be very full here, with the batter coming up almost the top of the cups. Generously sprinkle the tops with more sugar.
Bake for 16-20 minutes, or until the muffins are puffed, lightly golden brown, and a toothpick comes out with just a few crumbs on it. Once removed from the oven, use a butter knife to ensure that any overhanging parts don't stick to the pan. Cool the muffins completely in the pan, and enjoy!