Preheat the oven to 350 degrees F. Use butter or cooking spray to lightly grease your 9x5 inch loaf pan.
In a large bowl, mix the butter and sugar until fluffy. Stir in the eggs, one at a time, and mix everything well. Add your mashed bananas and vanilla extract to the butter mix.
In an additional large bowl, mix your flour, baking soda, and salt.
Add the flour mix to the butter mix and thoroughly combine; do not over mix.
Pour your mixture into the prepared loaf pan. Bake for 55-60 minutes or until a toothpick comes out clean when inserted in the middle.
Remove from the oven and let cool for several minutes before slicing and serving.