Transfer tomatoes, ginger and red chilli powder to a mixer jar and make a fine paste. Keep it aside.
In a big mixing bowl, combine sorghum flour, rice flour, refined flour and semolina.
Add tomato paste and 3 cups of water. Use a whisker to mix well and remove lumps. Cover and rest it for about 15 minutes.
After 15 minutes, add cumin seeds, crushed black pepper, chopped onion and fresh coriander leaves.
Add salt and 3 more cups of water. Mix well.
Heat a nonstick pan. Grease its surface with oil.
On medium heat, drop the batter on the pan, such that a thin layer of the batter is formed on the pan and pores appear.
Brush oil along the edge and on the dosa.
Let it fry for 30-40 seconds on medium heat or until you start seeing brown specs.
Flip it and fry for 10 seconds.
Remove from the pan and serve hot.
Follow the same steps to use the rest of the batter to make dosas.