Preheat the oven to 350 degrees F and line a muffin tray with 9 muffin papers.

Mash the bananas in a measuring cup until very creamy. Be sure you have around 1 cup of mashed banana. Transfer the mashed banana to a mixing bowl and add the eggs and grated apple. Whisk everything together until very well-combined.

In a separate bowl or measuring cup, stir together the almond flour, sea salt, baking powder, and ground cinnamon until combined. Transfer the flour mixture to the mixing bowl with the banana-apple mixture and stir well until combined.

Fill the muffin holes up ¾ of the way full with muffin batter. Bake on the center rack of the preheated oven for 30 to 35 minutes, until muffins are golden brown and feel firm when gently poked. Allow muffins to cool at least 30 minutes before unwrapping.