In a small bowl, mix together the milk alternative with the vinegar (we're making buttermilk). Set aside.
Whisk together the almond flour, tapioca flour, pectin, xanthan gum, sugar, salt, soda, and yeast... all the dry ingredients.
Add the eggs, butter, and vanilla to the milk mixture and mix well. Add the wet ingredients to the dry and knead with a dough hook until it comes together, scraping down bowl as needed. If you don't have a dough hook, mix together with a spoon the best you can and then use your hands to knead the dough until it is very well combined. Batter will be thick and sticky.
Scrape/pour batter into plastic wrap and wrap tightly. Place in refrigerator 6 hours to overnight.
Tear out a piece of parchment paper that is at least 20 inches long and sprinkle generously with arrowroot or tapioca flour. Using a well-floured rolling pin, roll the dough 15 inches (the height of the parchment paper) by 20 inches long. Use tapioca flour as needed to help prevent sticking.
Bring a medium to large pot of water to a boil... we'll come back to this :)
Melt the butter and spread over the dough, leaving the bottom 1 inch dry.
In a medium-sized bowl, mix together the cinnamon, sugar, and xanthan gum. Spread evenly over the butter.
Starting on the side farthest away from you, start rolling the dough tightly making at least 4 or 5 rotations. You can lift up the parchment paper to help get the dough up and rolling. When you come to the end, pinch the bottom edge of the dough into the log so it creates a seal.
Using a very sharp knife, cut the log in half. Then, cut each half in half. Then cut each roll in half again. You should have 16 rolls.
Transfer rolls to the baking dish and slightly press down on each roll.
Place rolls in center or top rack of oven with the boiling water on the bottom rack and allow to proof for 1 hour. They won't double in size but they will rise. I covered mine with a clean, damp kitchen towel.
Remove rolls and preheat oven to 350 degrees.
Bake for 16 - 20 minutes, rotating half-way through to ensure even baking. Make sure they are very nicely browned so the centers aren't dough-ey.
Whisk all ingredients in a large mixing bowl. Icing will be thick. Pour over hot rolls.