1. Preheat oven to 350. 
2. Line 24 muffin tins with paper liners.
3. In a small bowl, combine mashed bananas and lemon juice.  Set aside.  In a separate bowl, combine flour and baking soda.
4. In the bowl of your mixer, beat butter and sugar on medium speed until light and fluffy, about 2 minutes. 
5. Beat in eggs, one at a time, until combined. 
6. Add vanilla to the buttermilk. 
7. With your mixer on low speed, add your flour and buttermilk alternately, starting and ending with the flour mixture. 
8. Fold in mashed bananas.
9. Fill prepared muffin tins 2/3 full.  Bake for about 20 minutes, or until tops spring back when lightly touched.  Let cool completely on cooling rack.

Prepare frosting:
 

1. In the bowl of your mixer, beat cream cheese, butter, and vanilla on medium speed until smooth and combined. 
2. With the mixer on low, slowly add powdered sugar and cinnamon. 
3. Continue mixing on low until just combined. 
4. Increase speed to medium high and beat for about a minute, until fluffy. 
5. Frost cooled cupcakes.