Prep and preheat: Preheat oven to 350 degrees Fahrenheit, line a 9x5 loaf pan with parchment paper and set aside.
Combine dry ingredients: To a bowl add einkorn flour, baking powder, baking soda, salt, cinnamon and cardamon. Whisk and set aside.
Combine wet ingredients: To a bowl add in melted and cooled butter, maple syrup, room temperature eggs, room temperature sour cream, room temperature buttermilk and vanilla bean paste or extract. Whisk together until smooth and well combined.
Combine dry with wet ingredients: Gently fold in your dry ingredients to your wet mixture. Mix until just combined. Allow batter to rest while you make the cinnamon filling.
Make cinnamon filling: Combine melted butter, coconut sugar, maple sugar, cinnamon, cardamon and vanilla to a bowl and mix until it forms a course sandy texture.
Fill loaf pan: Pour half of the batter into the prepared loaf pan. Sprinkle a little more than half the cinnamon filling evenly over the batter. Add the remaining batter on top, then finish with the remaining cinnamon filling. Using a butter knife, gently swirl the batter down the length of the pan and back up once. Avoid over-swirling to keep the cinnamon layers distinct.
Bake: Bake in 350 degree Fahrenheit oven for 45-55 minutes or until a toothpick inserted comes out clean or with minimal crumbing.
Allow to cool and frost: Mix together the icing ingredients until well combined, the icing should be thick, pourable and able to ribbon off a spoon. Thin out more if needed or to thicken a tad add a bit more powdered sugar. Once the loaf has cooled pour over the top and allow to harden for 30 minutes. Slice and enjoy!