Add the cumin seeds, 1 chopped red onion, and shredded coconut along with some water to a blender and grind it to a thick paste. Keep it aside.
Heat oil in a saucepan at medium temperature, and add chopped tomatoes.
Add salt as required, then close with a lid and let the tomatoes cook for a few minutes.
Add the turmeric powder and chilli powder.
Cook until oil starts oozing out of chopped tomatoes, opening the lid and stirring intermittently.
Once oil starts oozing out of the tomatoes, add the ground masala from step 2 along with 1/4 cup water to the saucepan and some salt to taste, and give everything a good mix.
While the tomatoes are cooking, prepare some tempered onions according to steps 9 – 12.
Heat about 1 tbsp oil enough for tempering.
Add 1/2 tsp mustard seeds, and them to splutter before adding in 1/2 tsp urad dhal.
Once the urad dhal is slightly browned add 1/2 medium chopped onions, and a sprig of curry leaves.
Sauté everything and remove from heat.
Check to make sure the tomatoes are well cooked before adding the tempered onion mixture from steps 8 – 12 and give everything a good stir.