Combine the Urad and chana Dals with water, salt and turmeric, and cook under High Pressure for 30 minutes. You can use the BEAN setting on your Instant Pot for this.
Meanwhile, heat a nonstick pan on your stove, and when that's hot, add the ghee. When the ghee is hot and shimmering, add the chopped onion and sauté for 30 seconds. Add minced ginger and minced garlic and cook these aromatics for 5 minutes, until the edges of the onion start to brown slightly.
Add tomato and spices and mix well. Add water and mix again.
Crush the tomatoes with the back of your spoon as they cook. Set aside until the dals are cooked.
Once the dals are cooked, allow the pressure cooker to release pressure naturally for 10 minutes and release any remaining pressure.
Using your spoon, crush the dals well to get a creamier texture, leaving some whole dal in the mix.
Pour in the tomato and onion mixture and mix well before serving.