Sieve refined flour with baking powder, baking soda, salt in a bowl. Add sugar and 2 tbsp of butter into it and mix it well. Add curd and warm milk into it and knead it well and make a soft dough of it. Apply a little oil and keep it under wet cloth for 1 hour.
After 1 hour, knead it once and make equal sized balls of it and further roll it and add some onion seeds to it and then again roll it in oval shape and on its opposite side apply some water over it.
Heat a iron tawa, put the rolled naan from its side on which water is applied and stick it. Cook it for 20 seconds on that side and then reverse the tawa towards the flame side.
Cook it from away the flame on high flame. Again put the tawa on the flame and cook it nicely from both sides.
Take it out from the tawa, apply some butter combined with coriander leaves on it and serve it.