Step 1

In a medium bowl, mix together the chicken, chili powder, garam masala and 1 teaspoon each salt and black pepper; set aside. In a 12-inch skillet over medium-high, heat 1 tablespoon oil until barely smoking. Add half of the bell peppers and cook, stirring just once or twice, until lightly charred, 3 to 5 minutes. Transfer to a small bowl; set aside.

Step 2

To the same skillet over medium-high, combine the remaining 2 tablespoons oil and the cumin seeds. Cook, stirring often, until the seeds are fragrant and sizzling, about 30 seconds. Add the remaining bell peppers and the onion; cook, stirring often, until lightly browned, about 5 minutes. Add the garlic, ginger and chicken mixture. Cook, stirring, until fragrant, about 30 seconds. Add the tomatoes and bring to a simmer, scraping up any browned bits. Reduce to medium, cover and cook, stirring occasionally and adjusting the heat to maintain a gentle but steady simmer, until a skewer inserted into the chicken meets just a little resistance, 10 to 15 minutes.

Step 3

Uncover, increase to medium-high and cook, stirring occasionally, until the sauce is lightly thickened, about 5 minutes. Off heat, stir in the reserved bell peppers and the cilantro. Taste and season with salt and black pepper.