Add besan to a mixing bowl. Add salt and turmeric. Lightly crush carom seeds on the palm of your hands and add to the bowl. Add onion, tomato, green chili, ginger and cilantro.
Add water little bit at a time mixing the batter well. The batter should be smooth with a good pouring consistency.
Heat a griddle and apply oil.
Pour two small ladle full of batter, about ½ cup on the pan, and spread it gently in a circular motion using the back of the ladle or a spoon to make a 6-inch round chilla.
Cook for 3 to 4 minutes on medium heat. Drizzle ½ teaspoon of oil on top and around the edges.
Carefully flip over the chilla. Cook until the other side becomes lightly brown and the edges start to crisp. Take out the chilla.
Repeat the above steps to make Chillas with the remaining batter.