Not a bundt cake. But I think it is my most requested cake...
I have a very rich, dense, heavy banana cake that can be made into loaves, layers or sheet (I think originally from Pat in Tokyo). If you'd like the recipe - just let me know
I almost always have buttermilk in my fridge and not sour cream so I use buttermilk where the recipe calls for sour cream.
Also - when I make this as a bundt or layer cake I made a chocolate ganache layer (if bundt I cut into two layers and fill with the chocolate ganache. Although i'm sure you could also fill it with the ganache and back.
I don't know if it makes the cake more moist but for years I've been swapping it when a recipe calls for sour cream. Honestly I just like the taste so much