In a small bowl, mix the sugar, yeast and warm water. Let sit for 10 minutes until the mixture is foamy.
In a large bowl, combine the flour and salt. Make a well in the center and add in the yeast mixture, yogurt and oil. Mix together until it forms a dough.
Knead the dough for 10 minutes until it is soft and pliable. Cover with a damp cloth and let rise for 1 hour.
Divide the dough into 8 equal pieces and roll each piece into a ball. Let rest for 10 minutes.
Roll each ball of dough into an oval shape about 1/4 inch thick. Heat a skillet over medium-high heat and cook naan on each side until golden brown.
Remove from heat and brush with melted butter or ghee if desired.