Make the streusel: mix the brown sugar, flour, and cinnamon in a small bowl. Add the butter and work it in with fingers or a knife until mixture is crumbly. Set aside.
Preheat the oven to 400 degrees. Lightly grease 10 muffin tins. Melt the butter and set it aside. Mix the flour, baking soda, baking powder, salt, and cinnamon together in a bowl. In another bowl, mix the bananas, sugar, egg, and vanilla extract until well blended. Stir in the melted butter and cranberries. Spoon the flour mixture into the banana mixture and stir until just until combined. Spoon the batter into the prepared muffin tins. Sprinkle the streusel mixture evenly over each muffin. Bake for 18-20 minutes, or until a cake tester inserted into center of muffin comes out clean.
Ronnie Fein is a cookbook author, food writer and cooking teacher in Stamford. She is the author of The Modern Kosher Kitchen and Hip Kosher. Visit her food blog, Kitchen Vignettes, at www.ronniefein.com, friend on Facebook at RonnieVailFein, Twitter at @RonnieVFein, Instagram at RonnieVFein.