Preheat the oven to 300 degrees Fahrenheit and lightly brush a shallow oven tray with a little coconut oil.
Add the ground almonds to a food processor along with 1 and a half teaspoons of cinnamon, 2 eggs, flaxseed, lemon juice, 1 teaspoon of vanilla extract, ¼ cup of erythritol, coconut flour, baking soda and salt.
Blend to form a dough.
Divide the dough evenly into four portions and form into buns. Whisk the egg yolk and brush liberally all over the buns.
Transfer to the oven to bake for 20-22 minutes until cooked through and golden brown all over.
Whilst the buns are baking you can prepare the cinnamon icing. Add the almond milk to a small pan along with the almond butter, remaining cinnamon, remaining erythritol, and remaining vanilla.
Bring to a boil then reduce to a simmer for 5-6 minutes until you have a thick golden icing.
Remove the buns from the oven and allow to cool completely. Slice in half and slather with butter then reassemble and top with a generous helping of icing.