In a large mixing bowl, mash the bananas. Add the brown sugar, butter and eggs and beat until fully incorporated.
Add the baking soda, salt, and cream of tartar. Add flour, 1/2 cup at a time, just until incorporated.
In a small mixing bowl stir together the cinnamon and sugar.
Grease a regular size loaf pan. Sprinkle 1/4 cup of the cinnamon sugar mixture into the bottom of the pan. Pour half the batter into the pan. Sprinkle another 1/4 cup of the cinnamon sugar on top of the batter. Scoop in the remaining batter into the pan and sprinkle the remaining cinnamon sugar mixture on top, reserving 1-2 tablespoons.
Bake at 350 degrees F for 45 minutes to 1 hour or until a toothpick comes out clean. Sprinkle the remaining cinnamon sugar mixture on top. Allow the loaf to cool for about 5 minutes. Remove onto a cooling rack to cool completely. Slice and enjoy!