Preheat your oven to 350-F and spray a 10-cup bundt pan with cooking spray then lightly flour it.
Whisk together the all-purpose flour, baking powder, nutmeg, cinnamon and salt in a large bowl.
Cream the butter in the bowl of a stand mixer with the paddle attachment until light and fluffy, about 2 minutes.
Add the white and brown sugar, beating until light.
Add the eggs to the butter and sugar mixture, one at a time, mixing well in between each egg. Add the vanilla along with the last egg.
Add half the flour mixture and half the buttermilk to the bowl of the stand mixer and mix until combined.
Add the remaining flour and buttermilk and mix.
Mix in the smashed bananas and mix until just combined. Don't overmix.
Transfer the batter to the prepared bundt pan and bake until cooked.
Cool on a wire rack until cool enough to handle, then invert the pan onto a plate and cool the cake completely before glazing.
Make the glaze by beating together the butter and cream cheese until well mixed. Turn off the mixer and add the powdered sugar and 1 tablespoon of milk. Mix, adding a dribble more milk as needed until the glaze is runny but still thick.
Glaze the cake with the cream cheese glaze, slice and serve!