Firstly, in a large bowl take 2 onion, 2 tomatoes,2 chillies, 1-inch ginger, few curry leaves, 2 tbsp coriander and ½ tsp salt.
mix well making sure everything is well combined., also, heat the griddle and pour a ladleful of dosa batter.

Spread out in a circular motion slightly thick than regular masala dosa.
now spread the toppings on top of the uttappam evenly.
after the topping have been added press gently so the toppings are pressed into the batter.

Add 1 tsp of oil around the uttapam.
cover it and let it cook for 1-2 minutes in low flame.
flip over on the other side once the uttappa turns golden brown.

Tomato onion uttapa is ready to serve with sambhar.