I actually do, sometimes, just whip this up; I usually have the ingredients on hand.
3 overripe bananas, smashed with a fork in a bowl
1/3 cup melted butter (microwave ~40 seconds!)
1 teaspoon baking soda
Pinch of salt
1/2 cup brown sugar
1 beaten egg
1 teaspoon vanilla
1 1/2 cups flour
1/2 cup of walnuts, chopped a bit
Preheat the oven to 350F, and butter a 4×8-inch loaf pan. Mash the ripe bananas with a fork until smooth, and then stir the melted butter into the mashed bananas. Now add the baking soda and salt. Stir in the sugar, beaten egg, and vanilla extract. Add and stir in the flour. And the walnuts.
Pour and scrape the batter into the buttered pan, and bake for 45 minutes to 1 hour (which means start checking at 45 minutes). When a toothpick comes out clean, remove the loaf from the oven and let it cool on a rack. Remove the banana bread from the pan.
Slice and serve. It’s best when it’s still a bit warm: add a spread of butter for even better flavor. (It’s also best toasted with butter the next day.)