Add the almond flour, coconut flour, xanthan gum, baking powder and salt to a food processor. Pulse a few times until evenly combined.
With the processor running, pour in the apple cider vinegar, then add the egg and the water. Process until the dough comes together into a ball. If it looks dry and crumbly, add 1 more tsp of water.
Knead the dough in your hands for 1 minute until smooth. Wrap it tightly and let it rest for 10 minutes so the flours can hydrate.
Divide the dough into 8 equal balls. Roll each ball between two sheets of parchment paper into a thin 5-6 inch round.
Heat a dry cast iron or nonstick skillet over medium-high heat until very hot. Cook each tortilla for 20-40 seconds per side, until it puffs slightly and light charred spots appear.
Stack the cooked tortillas under a clean kitchen towel to keep them warm, soft and pliable until serving.