Rinse and drain the rice thoroughly.
Heat oil in a medium pan over medium heat. Add the rice and stir continuously for 5–6 minutes or until golden brown and lightly toasted.
Reduce heat to medium-low, add the blended tomato mixture, stir to combine, and season with salt, stirring until dissolved.
Make a cut along the tip of a serrano pepper, stopping before the stem (don’t cut through it). Place the pepper in the center of the pan and cover with a lid.
Simmer gently until the liquid is absorbed and the rice is tender, about 20 minutes, taking care not to lift the lid too often.
Remove from heat. You may notice a thin film on the surface—gently fold it into the rice. Cover again and let the rice rest for 10 minutes.
Fluff the rice with a fork and serve.