Dry fry the cumin and mustard seeds in a large sauté pan until the start to make a popping sound. Remove from heat and grind them in a spice grinder or mortar and pestle.
If you are using fresh chicken, season the chicken with salt, pepper, and curry powder. Add the oil to the pan and brown the chicken in batches, transfer to a plate. You don’t have to cook it all the way through as you will continue to cook it as it simmers.
Add the onion, garlic, and ginger to the pan. Cook until they soften, about 4 minutes.
Add the cumin, mustard seed, chili, curry paste, coriander, turmeric, and tomato paste. Cook, while stirring, for about 1 to 2 minutes. It will make a thick paste.
Add pour in the water, scraping up the bits on the bottom of the pan. Add the chicken (the browned chicken or your fully cooked chicken) and simmer on medium-low heat for 20 to 25 minutes longer.
Add red peppers and squeeze of lime, cook for another 3 minutes.
Serve over rice and top with desired condiments.