Preheat oven to 350° Prepare cake pans or cupcake trays (grease and flour or use liners respectively)
In a separate bowl: sift together dry ingredients and set aside. (flour, salt, cardamom and baking soda)
In your mixer bowl: cream the butter and gradually add in the sugar.
Add in the eggs, beat thoroughly.
Add mashed banana and vanilla. Mix well
Add the flour mixture to the banana mixture alternating with the sour cream. Work it so you end with the sour cream. Mix a little after each addition.
Put batter into your chosen pan and bake
20 minutes for cupcakes and 40 minutes for 9" pans. Rotate your pans halfway through if you have hotspots. Check your cakes at 10 minute intervals because ovens vary and you don't want to over bake.