Preheat oven to 400º. Line 12 muffin pan cups with paper liners.
In a large bowl, stir together flour, 1/2 cup of the sugar, baking powder, baking soda, and salt. In a medium bowl, stir together egg, yogurt and vanila, pour over dry ingredients. Add melted butter and stir just to blend (do not overmix). Quickly spoon batter into paper liners, filling each muffin cup to the top. Sprinkle with remaining 1 tbsp of sugar.
Bake muffins about 20 minutes, or until a toothpick inserted in center comes out clean. Remove muffins to wire rack and let cool 10-15 minutes before serving.