Preheat oven to 400 degrees. In a large bowl, stir together flour, 2/3 cup sugar, baking powder, baking soda and salt. In another bowl, blend yogurt, butter, egg, lemon zest and vanilla. Make a well in the center of dry ingredients and add yogurt mixture; stir just to combine. Stir in blueberries. Spoon batter into greased muffin cups and sprinkle with the remaining 1 tablespoon sugar. Bake 20 to 25 minutes or until a cake tester inserted in the center of one muffin comes out clean. Cool muffins for 5 minutes in the muffin tin on a wire rack. Remove muffins to rack and cool. Serve warm or cool. NOTE: Use real butter or stick margarine. Do not substitute reduced fat spreads; their higher water content often yields less- satisfactory results.