Combine warm water, sugar, and yeast in a small bowl; let stand for 5 to 10 minutes until foamy.

In a large mixing bowl, whisk together 2 cups of flour and the salt.

Create a well in the center of the flour and pour in the yeast mixture, yogurt, olive oil, and egg.

Stir the ingredients together, gradually adding the remaining flour as needed, until a soft, slightly tacky dough forms.

Knead the dough on a lightly floured surface for 3 to 5 minutes until smooth and elastic.

Place the dough in a lightly greased bowl, cover with a damp cloth, and let rise in a warm, draft-free area for 60 minutes or until doubled in size.

Punch down the dough and divide it into 8 equal-sized balls.

Using a rolling pin, flatten each ball into an oval shape approximately 1/4 inch thick.

Heat a heavy cast-iron skillet over medium-high heat and lightly brush with oil or butter.

Place one piece of dough in the hot skillet and cook for 1 to 2 minutes, or until bubbles form on the surface and the bottom is golden brown with dark spots.

Flip the naan and cook the second side for an additional 1 to 2 minutes until browned.

Remove from the pan and immediately brush with melted butter and sprinkle with cilantro if desired.