Add the sugar, salt and egg to a mixing bowl and stir until well combined. Slowly drizzle in the margarine, stirring constantly. Then add the cinnamon and stir to combine.

Separately, mix the baking soda and water and add them to the large mixing bowl. Add the flour and stir until just moistened, then add the mashed bananas and stir again.

Drop in the blueberries and carefully stir with a spatula to combine.

Pour the batter in to a prepared loaf pan and set it aside while making the streusel topping.

Mix the flour, brown sugar, and oatmeal then add the melted margarine. Spread the mixture over the banana blueberry bread batter and place the pan in the oven at 350 degrees for 50-60 minutes. Insert a toothpick to make sure the cake is done.

Enjoy!