Activate the Yeast: Combine 1/4 cup warm milk (110F), 1 teaspoon sugar, and 2 1/4 teaspoons yeast. Let sit 5 to 10 minutes until foamy.
Make the Dough: Whisk 3 cups flour, 1 teaspoon salt, and 1/2 teaspoon baking powder. Add yogurt and yeast mixture. Mix and knead 8 to 10 minutes until smooth and elastic.
Let the Dough Rise: Place in a greased bowl, cover, and let rise 1 to 2 hours until doubled in size.
Shape the Naan: Punch down the dough and divide into 6 to 8 portions. Roll each into an oval, about 1/4 inch thick.
Cook on the Stovetop: Heat a cast-iron skillet over medium-high heat. Cook naan 30 to 45 seconds per side until bubbles form and char spots appear.
Finish with Butter: Brush hot naan immediately with melted butter. Serve hot.