In a large skillet set over medium heat, heat the oil until shimmering, about 2 minutes. Add the rice and serranos, and cook, continually stirring, until lightly browned, taking care not to burn the rice, 10 to 15 minutes.
Add the stock (it will make a loud sizzling noise, so stand back a bit), the onion, tomato, cilantro, bell pepper, cumin, garlic, salt and pepper. Increase the heat to high and bring to a boil. Taste the juice with a spoon and season to your liking.
Reduce the heat to low, cover, and simmer for 15 minutes. (Do not uncover during cooking.) Remove the serranos and discard. Fluff and serve, garnished will a little more cilantro.