In a small bowl, combine the flour, 1/4 cup sugar, baking powder, baking soda and salt. In another bowl, whisk the sour cream, oil and egg; stir into dry ingredients just until moistened. Fold in raisins.
Fill six greased or paper-lined muffin cups half full. Sprinkle with remaining sugar. Bake at 400° for 15-18 minutes or until a toothpick inserted near the center comes out clean. Cool for 5 minutes before removing to a wire rack. Serve warm. Yield: 6 muffins.