YIELD = 12 SERVINGS
Preheat oven to 350°F/180°C. Grease a 9" x 5" loaf pan. Line with wax paper. Grease paper. Mash bananas in a large bowl. Stir in buttermilk, melted margarine and sugar. Set aside. In a medium bowl, combine dry ingredients; flour, cinnamon, baking powder salt and baking soda.
Blend into bananas in batches, mixing well after each addition. Add eggs and mix well. Gently fold in blueberries. Pour into prepared pan, spreading evenly. Bake until tester inserted in the center comes out clean. (60-70 minutes).
Cool on a rack for 10 minutes. Turn out of pan onto rack, remove the wax paper. Cool completely. For easier slicing, wrap well and store overnight.