In a medium bowl add the flour, cream of tartar, salt, and sugar and whisk to combine well. Add the yeast and whisk one more time. Add the yogurt, melted butter and water, and either with your hands or with a stand mixer fitted with the paddle attachment mix on medium speed for about 3 minutes. The dough should be a little bit sticky. If you are using a mixer you will need to pull away from the sides of the bowl in spots. Because It will not turn into a fully integrated ball of dough on its own.
Press the dough into a ball, cover it and place it in a warm spot to rise until it doubles in volume (for about 40 minutes)
Once the dough has finished rising, turn it out onto a lightly floured surface and sprinkle lightly with more flour. Divide the dough into 8 pieces. Working with one piece of dough at a time, lightly flour it and roll it into an oval shape about 3/8 inch thick.
If you are using butter for frying. First, melt it in a separate pan. Then brush one side of the bread. Place the bread buttered side down on a heated skillet. While it is frying on the side brush the top side with butter or oil. Fry on one side until large blisters begin to form (about 30 seconds) then flip it on the other side for another 20 to 30 seconds.
Remove to a paper towel or tea towel, and cover the dough to retain the heat and moisture.
Repeat with the remaining pieces of dough.
Stack the pieces of naan one on top of another, keeping them covered with a tea towel to maintain freshness
Best served warm.