Instructions
Mix the dry ingredients & the onion
Put the ragi flour, salt, cumin seeds, chopped onion, green chilli, coriander and coconut into a wide bowl. Rub the onion into the flour with your fingertips for a minute. The salt pulls water out of the onion, and that moisture is part of the dough — not a garnish.
Bring the dough together
Add water a few tablespoons at a time, mixing as you go. You want a soft dough that just holds together — noticeably softer than chapati dough, closer to modelling clay. Roughly ¾ cup suits 1½ cups of flour, but a coarse grind and a juicy onion both shift that, so go by feel rather than by the measure. Cover and rest for 10 minutes.
Pat it on a cold tawa
Lightly oil a cold tawa. Wet your palm, take a lemon-sized ball of dough and press it onto the pan, working outward from the centre with wet fingertips until it is about 15 cm across and thinner at the rim. Re-wet your fingers the moment the dough starts sticking. Starting cold is what stops raw dough gluing itself to the pan — a hot tawa here is the single most common mistake.
Make the steam holes
Poke three or four holes right through the rotti with a fingertip. They let steam out of the middle so the centre cooks at the same rate as the rim, instead of ballooning and tearing.
Cook covered
Now put the tawa on medium heat. Drizzle half a teaspoon of oil around the rim and into the holes, cover, and cook about 3 minutes — until the surface loses its wet sheen and the underside has brown spots.
Flip & finish
Flip the rotti, press gently all over with a folded cloth, and cook uncovered for another minute or two. Serve hot with coconut chutney, ennegayi (stuffed brinjal) or plain curd.