Rinse raw rice and urad dal separately. Soak them separately in enough water for minimum 3 to 4 hours. You could also soak them over night.
Next morning, grind both rice and urad dal together with little water until it forms a smooth batter. Add roughly chopped tomatoes and grind for few more minutes till all tomatoes are ground well.
Pour batter into a bowl. Add salt to taste and mix well. Add cooking soda and mix again. Leave it for 10 minutes.
Heat a non stick tawa. Pour a ladle full of batter and spread it into round dosa shape. You can spread it thin or leave it a little thick.
Dribble a few drops of oil or ghee on the sides. Cover it with a pan and let it cook on low flame.
Once the sides of the dosa starts to brown and release from the pan, gently remove dosa from tawa. Repeat the same with rest of the batter.
Serve dosa immediately hot with coconut chutney, spicy onion-tomato chutney or even chutney powder.
Notes
You can use red rice in place of raw rice for this dosa. I haven't used brown rice for dosa batter, but i'm guessing brown rice will work too. Need to check the texture and taste of the dosa with brown rice.