Prepare the batter by soaking 2 cups of rice and 1 cup of urad dal (split black gram) separately for 4-6 hours. Drain the water and grind them separately into a smooth paste. Mix both the pastes together, add salt to taste, and let it ferment overnight.
Finely chop 2-3 medium-sized tomatoes, 1 medium-sized onion, 1 green chili, and a handful of fresh coriander leaves.
Heat a non-stick tawa or griddle over medium heat. Pour a ladleful of the fermented batter onto the tawa and spread it evenly in a circular motion to form a thick pancake.
Sprinkle the chopped tomatoes, onions, green chili, and coriander leaves evenly over the batter. Gently press the toppings into the batter using a spatula.
Drizzle 1 teaspoon of oil around the edges of the uttapam and cook for 2-3 minutes or until the bottom turns golden brown.
Flip the uttapam carefully and cook the other side for another 2-3 minutes or until it turns golden brown.
Remove the uttapam from the tawa and serve hot with coconut chutney and sambar.