Preheat the oven to 375°F. Grease a nonstick 10-cup bundt pan with cooking spray.
In a small bowl, combine the mashed bananas with the lemon juice and set aside.
In a separate bowl, whisk together the flour, baking soda and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together the butter and the sugar until light and fluffy, then beat in the eggs one at a time.
Add the vanilla and then beat in the flour mixture alternately with the buttermilk.
Fold in the mashed banana mixture and then the chocolate chips.
Bake the cake until a toothpick inserted comes out clean, 40 to 50 minutes. Remove the cake from the oven and let it cool completely in the pan before inverting it onto a serving platter.