Preheat oven to 375°. In large bowl, cream butter, sugar, and lemon until light, about 5 minutes. Beat in egg and vanilla. Mash 1/4 cup of the berries. Beat into batter. Whisk together flour, baking powder and salt. Fold into batter alternately with milk. Fold in blueberries. Spoon into 8 paper lined muffin cups.
Place Topping in small strainer and dust each muffin.
Bake until muffins spring back when lightly touched, 20 to 25 minutes. Serve warm or at room temperature.