I didn't have any baking soda except the kind in the deodorizing boxes; however, upon googling I learned two facts 1) they're the same thing and 2) you cannot leave it out and still get normal muffins.
4 ripe bananas, smashed
1/3 cup melted butter
3/4 cup sugar
1 egg, beaten
1 teaspoon vanilla
1 teaspoon baking soda
pinch of salt
1 1/2 cups of all-purpose flour
Preheat the oven to 350°F (175°C).
With a wooden spoon (no need for a mixer for this recipe), 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, and mix.
Pour mixture into a buttered muffin pan. Bake for 1/2 hour.