First, please make sure all your ingredients are at room temperature. If your eggs are fridge cold, submerge them in a bowl of very warm water for 5 minutes. If the maple syrup is cold, measure out ¼ cup, put the measuring glass in a bowl and fill the bowl with very warm water until it reaches the height of the maple syrup. Let it sit for about 5 minutes.
Heat the oven to 350° F.
Line the long sides of a 9x5" loaf pan with parchment paper with some coming up just past the top of the pan. Spray the short sides with cooking spray.
In a small bowl, melt the palm shortening in a microwave, about 1 minute. Or you can melt it in a small saucepan over medium heat, then scrape into a small bowl. Set aside to cool.
In a large bowl, whisk together the almond flour, arrowroot, cream of tartar, cinnamon, salt and baking soda.
In a medium bowl, use a fork or potato masher to mash the bananas until fairly smooth. Measure out 1 cup.
In another medium bowl, whisk together the eggs, maple syrup, melted and cooled palm shortening, vanilla and 1 cup of mashed bananas.
Stir the wet ingredients into the dry ingredients until smooth and well-blended. The batter should be thick but pourable.
Scrape into the prepared loaf pan and smooth the top into an even layer. Bake for 50-55 minutes, until the top is dry and golden brown. (Don't bother with a toothpick - it'll come out clean even after 30 minutes but that doesn't mean the bread is done yet.) Let cool completely.