Combine almond flour, coconut flour, psyllium, baking soda, and sea salt in a medium bowl. Set aside.
In large mixing bowl, stir together hot water, egg whites, and apple cider.
Stir the dry mixture into the liquid mix. It will thicken as it sits. Once thickened, divide dough into 15 pieces for small keto buns or 8 pieces for larger hamburger buns.
Form each piece into a bun (if dough is too sticky, it helps to use wet hands) and place on prepared baking pan.
Bake for 25-30 minutes or until edges are browned and centers are set.
Place pan on rack to cool for 10-15 minutes and then remove the rolls from the pan and place directly on the rack to cool completely.
Nutritional data is for the smaller buns assuming the recipe makes 15.Line the baking sheet with a silicone baking mat. This will prevent the rolls from sticking to your baking tray and it makes clean-up easier too.Don't forget to let the batter thicken before you form the buns. The batter will be thin at first but it will thicken the longer you let it sit at room temperature.If the dough is too sticky to form into rolls, dampen your hands with water. The batter won't stick as well to wet hands.