Heat the vegetable oil in a large skillet or pot over medium heat. Add the cumin seeds and let them sizzle for about 30 seconds until fragrant.
Add the chopped onion and sauté until golden brown, about 5-7 minutes.
Stir in the minced garlic, ginger, and green chilies. Cook for another 2-3 minutes until fragrant.
Add the coriander powder, turmeric powder, garam masala, and red chili powder. Stir well and cook for 1-2 minutes to toast the spices.
Add the chicken pieces to the pot, stirring to coat them with the spice mixture. Cook for about 5-7 minutes until the chicken is browned on all sides.
Pour in the drained diced tomatoes and chicken broth. Stir to combine, then season with salt to taste.
Bring the mixture to a simmer, then reduce the heat to low. Cover and cook for 25-30 minutes, stirring occasionally, until the chicken is tender and the sauce has thickened.
Taste and adjust seasoning if necessary. Garnish with fresh cilantro before serving.