Preheat the oven to 350 degrees Fahrenheit and line a muffin tin with muffin liners (this recipe makes 9 muffins).
Blend the oats in a high-speed blender or food processor for 20 to 30 seconds, or until a flour forms.
Mash the bananas in a large bowl, then add the eggs, oil, vanilla extract and vinegar. Beat these ingredients together until well-combined.
Transfer the dry ingredients (oat flour, baking soda, sea salt, and cinnamon) to the mixing bowl with the wet ingredients. Stir until a thick muffin batter forms. Add the chopped apples and stir well to combine.
Transfer the batter to the lined muffin tray, filling the holes almost all the way up. If you’d like, sprinkle with sliced almonds.
Bake on the center rack of the preheated oven for 30 to 35 minutes, or until the muffins are golden brown and test clean.
Allow the muffins to cool completely before you remove them from the muffin pan and peel them.
Peeling muffins when they’re still warm will result in them sticking to the muffin papers and a lot of muffin will be lost to the paper.
8. Enjoy these muffins warm with a pat of butter and a drizzle of honey with a cup of coffee or a mug of tea.