How to Make It
In a glass measuring cup, combine the yeast, sugar, and water and let sit for 10 minutes. In the meantime, mix the flour, baking soda, and baking powder in a large bowl.
Whisk together the yeast mixture, yogurt, and milk, and stir into the dry ingredients. Knead with your hands until the dough forms a smooth, soft ball, about 2 minutes. Place the dough in an oiled bowl and cover with plastic wrap. Leave at room temperature until doubled in size, about 2 hours.
Remove the dough from the bowl and turn onto a well-floured surface. Knead it briefly and divide the dough into 12 equal portions. Roll it into 1/4-inch thick ovals, approximately 6 inches wide.
Heat a cast-iron skillet over moderately high heat. Brush each naan portion with melted butter and place in the skillet. Cook for about one minute, until dough puffs up. Flip, cover the pan, and cook for one more minute. Remove from the pan and brush both sides with butter and sprinkle with salt. Place in a towel-lined bowl until ready to serve.