Heat oven to 375 degrees. Grease 12 muffin tin or line with cupcake liners.
In a medium bowl, mash bananas and set aside.
Rinse blueberries and set aside. If using frozen blueberries, let stand for 10 minutes so that they thaw.
Combine cane sugar and butter in a large bowl. Beat well for 2 minutes on high. Add egg and vanilla. Beat for another minute.
Combine flour and baking powder in a small bowl. Add to batter alternately with milk. Beat well together.
Stir in mashed banana. Stir in blueberries. Mix well.
Fill muffin tins to the top.
Bake at 375 for 18 to 20 minutes or until toothpick inserted in center comes out clean.
While muffins are baking, combine cinnamon and the 3 tsp. of cane sugar.
Sprinkle tops of muffins with cinnamon/sugar.