Preheat the oven to 425°F and line a 12 cup muffin pan with paper liners.
In a large mixing bowl, combine the dry ingredients and mix well with a flat whisk until evenly combined; set aside.
In a seperate bowl, combine the bananas, buttermilk and avocado oil; mash the bananas roughly with a whisk (or potato masher) and then mix until all the ingredients are well combined.
Add the eggs and whisk until very well incorporated, about 30 seconds.
Throw in the dry ingredients and mix delicately with a rubber spatula until just incorporated, no more.
Divide the batter equally between the muffin cups; the batter will mound slightly higher than the paper cups, that's perfectly normal. If you preferred smaller muffins, you could also divide the batter between 18 to 24 paper cups, instead. Of course, you'd need to adjust cooking time accordingly.
Place the pan in the 425°F oven for 10 minutes and then lower the oven temperature to 375°F. Bake for another 8 to 10 minutes, or until the tops are nice and golden brown and a toothpick inserted in the center of a muffin comes out clean.
Let the muffins cool for a few seconds in the pan and then remove them to a cooling rack to cool completely.
Store in a cool dry place in an airtight container for up to a week.