Preheat oven to 350 degrees. With a wooden spoon,
mix butter into the mashed bananas in a large
mixing bowl. Mix in the sugar, egg and vanilla.
Sprinkle the baking soda and salt over the mixture
and mix in. Add the flour last, mix. Pour the
mixture into a buttered 4 x 8 inch loaf pan. Bake
for 1 hour. Cool on a rack.