Preheat your oven to 350 F.
In a large bowl, whisk together the applesauce, maple syrup, eggs, vanilla and olive oil.
Fold in the almond flour, oat flour, baking powder, baking soda, salt and cinnamon. Stir together until its fully incorporated.
In a small bowl, mix together the ingredients for the cinnamon swirl.
Line a 9 x 5 loaf pan with parchment paper. Pour half of the batter into the pan. Sprinkle the cinnamon sugar over the batter and swirl it in with a toothpick. Cover with remaining batter and gently spread it over with a spatula.
In a small bowl, prepare your crumble by mixing together the oat flour, coconut sugar and cinnamon. Add in the cold butter, and start mixing it together with a fork to create clumps. Once the butter is broken up, you can use your hands to create the crumbs.
Sprinkle the crumb topping over the center of the loaf.
Bake the loaf for 40-45 minutes, until the edges start to brown and a toothpick comes out clean from the center. While it bakes, mix together your icing ingredients until a thick glaze forms.
Let the loaf cool completely for 10-15 minutes, and top of with the icing if using.
Keep stored in a cool place for up to a week, or freeze for up to 2 months.