Preheat oven to 350F and line and grease a 12-tin muffin tray, plus a 6 if you have one (Note: if you are working in batches, you can place the mixture in the fridge, but once the first batch of muffins are cooling pull the dough out to bring them back to room temperature).
Whisk together in a large bowl the self-rising flour, ground cinnamon and sea salt, set aside.
Add bananas, buttermilk, brown sugar, sour cream, and vanilla to the bowl of a stand mixer and blend.
Add in eggs and mix until combined.
Slowly add in dry ingredients to incorporate.
Divide evenly into 18 muffins and bake for 15-18 minutes.
Cool on a wire rack for about 10-15 minutes before taking the muffins out of the tin. Enjoy!
Notes
Do not overbake the muffins or overmix your batter. Overmixing the batter will result in dry, crumbly muffins. Use the toothpick method to check for doneness with your muffins as every oven heats differently and some may be done sooner than others.
Store the muffins covered with an air-tight lid or sealed in a large ziptop bag at room temperature for 4-5 days. I don't recommend refrigerating these muffins as it can cause them to become dry and crumbly.
To freeze, allow the muffins to cool completely then wrap them individually in plastic wrap. Place them inside a large ziptop bag or air-tight container and freeze for up to 3 months.
Feel free to fold in about 1/2 - 1 cup of chopped walnuts to the batter for added crunch and flavor. Pecans, cashews, macadamia nuts, or chocolate chips are also great mix-in options.
Your bananas can be black, brown, or yellow with brown spots – so long as the banana is nice and ripe your muffin will come out tasty. When the banana peel has developed freckles, they are ready. The riper the banana, the stronger the banana flavor in your finished muffin. Dark/black bananas are perfectly okay to use.