Heat two-three cups of water in a pan till lukewarm. Place tawa on low heat. Mix together a fourth of the bajra flour and salt to taste and knead into a semi-hard dough using lukewarm water.
Roll into a ball. Dampen the palms. Place ball between palms and pat into the shape of a roti Place on moderately hot tawa.
Cook on one side and flip. Continue cooking till it puffs up. Remove from heat and serve hot with butter. Continue the same procedure with the remaining flour.