Preheat oven to 350 °F. Line 2-ounce size muffin pans with paper cups.
In a bowl sift together flour, baking soda and salt. Set aside.
Combine bananas and sour cream in a separate bowl. Set aside.
In a bowl, cream butter, sugar and vanilla until light.
Add the eggs, one at a time, mixing well for 30 seconds before adding the next one.
At low speed alternately add sifted dry ingredients and banana mixture to the creamed butter.
Scoop batter into muffin pans three-fourths full, bake for about 25 minutes or until the top springs back when lightly touched. Cool. Dust top with powdered sugar.