Preheat oven to 400°.
. Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and next 4 ingredients in a medium bowl; stir well with a whisk. Add blueberries and 2 teaspoons lemon rind; toss gently. Make a well in center of mixture.
. Combine buttermilk, butter, 1 teaspoon lemon juice, and egg in a bowl; stir well with a whisk.Add to flour mixture, stirring just until moist. Spoon batter into 12 muffin cups coated with cooking spray.
. Bake at 400° for 17 to 18 minutes or until golden brown. Remove muffins from pan immediately; cool on a wire rack.
. Combine powdered sugar, remaining 1 teaspoon lemon rind, and remaining 2 teaspoons lemon juice in a small bowl; stir until smooth. Drizzle glaze evenly over muffins.