Mix blueberry muffin mix according to package directions.
Add zest on one lemon and a teaspoon of fresh lemon juice to muffin batter.
Bake muffins according to package directions.
Mix powdered sugar and 2-3 tablespoons (more or less) fresh squeezed lemon juice to desired consistency.
Drizzle warm or cooled (if you can wait) muffins with glaze.