Start by prepping your stand mixer with the paddle attachment. Then add the flour, xanthan gum (if needed), salt, cream of tartar, and sugar to the bowl. Give it a good mix to combine well. Next, add the yeast and give it a solid stir before adding the yogurt, butter/ghee, egg and egg white, and water. Mix this on low until just combined.
When the mixture combines, turn the mixer up to medium and let it mix for at least three minutes. The dough should be light and fluffy while still coming away from the edges. It might not look like a traditional dough right now, and that's okay.
When the dough is done mixing, scrape the sides and roll the dough into a ball before placing it in a greased bucket with a lid or tight cover. Then allow the dough to rise until doubled in size, which should take about 45 minutes.
After the dough has finished rising, turn it out onto a lightly floured surface. The dough is going to be kind of sticky, so it's okay to use extra flour as needed. Next, divide the dough into eight pieces. Then, using one piece at a time, roll each piece into an oval about 3/8" thick.
To cook the naan, put a tablespoon of ghee or coconut oil into the cast iron skillet and melt over medium-low heat. When the ghee is melted, add the naan, one piece at a time, and fry until large air bubbles form. Then flip and repeat until you have a golden brown naan. Repeat until all pieces have been cooked to gluten-free perfection!