Dosa flour is flour of rice, urad dal and toovar dal. It is off white in colour. To Prepare Dosa Flour at home follow simple method. Wash and mix all the dals, soak for at least 5 to 6 hours and then blend into a smooth pancake-like mixture. Leave to ferment overnight in a warm place. Ensure the batter is of pouring consistency. Dosa flour is a boon for people who don't have the time to spend in the kitchen and want easy alternatives.