Grease the bottom of your loaf pan. If your pan is smaller, you may need more than one for the batter. Preheat your oven to 350℉.
Combine the flour, baking soda, and cinnamon in a bowl and set aside.
In your mixer (or by hand if you're powerful), cream together the melted butter and the sugars until it's smooth and fluffy.
Beat in the eggs until fully mixed.
Add in the buttermilk, bananas, and vanilla and combine.
Add in the flour mixture and beat together until about half mixed. Add in your nuts and any other mix-ins and finish mixing.
Pour your batter into your loaf pan and spread it out evenly.
Bake for an hour and 20 minutes. The top should be browned and cracking. If you want, you can check the internal temperature with a thermometer; you're looking for about 205℉.
Remove from the oven. Let the loaf cool for about five minutes, then flip it out of the loaf pan and let it cool to your ideal serving temperature.