1. Preheat oven to 350°. Place butter in an 8-inch square metal baking pan; place pan in oven 3 minutes or until butter melts.
2. While butter melts, weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, 6 tablespoons sugar, baking powder, and salt in medium bowl; stir with a whisk until blended. Combine milk, lemon rind, and vanilla; add to flour mixture, stirring with a whisk just until moist.
3. Pour batter over melted butter in pan (do not stir); top with blueberries. Sprinkle with remaining 2 tablespoons sugar. Bake at 350° for 35 to 40 minutes or until bubbly and crust is lightly browned. Serve with ice cream.