1In a bowl, combine flour, 1/2 cup sugar, baking powder, 1 teaspoon cinnamon and salt. Combine egg, buttermilk and butter: stir into dry ingredients just until moistened. Spoon 1 tablespoonful of batter into nine greased or paper-lined muffin cups. Combine rhubarb and preserves; place 1 tablespoonful in the center of each cup (do not spread). Top with remaining batter. Combine remaining sugar and cinnamon; sprinkle over batter. Bake at 400* for 20 minutes or until top of muffin springs back when lightly touched in the center.