Spray large loaf pans evenly with vegetable pan spray.
Melt the butter in microwave and add the sugar. Mix for a few minutes. Stir in the eggs, vanilla, and pureed bananas.
Combine together flour, salt, cinnamon, baking soda, and walnuts. Stir into the butter mixture.
Transfer batter into the prepared pans. If you are using mini loaf pans, fill them only 3/4 full.
Bake at 350°F for about 50 minutes for large loaves and about 30 minutes for mini loaves or until baked through. Use a toothpick to check for doneness - insert toothpick in center of pan, if toothpick comes out clean it's done.
Unmold pans as quickly as possible and let cool on cake rack (bread will get wet if they let cool in the pans).