Rinse rice until water runs clear; set aside.
Heat oil in a large saucepan over medium-high heat.
Add rice; cook, stirring, until lightly golden (about 10 minutes).
Add tomato sauce, garlic, and diced onion; stir.
Add tomato bouillon, salt, carrots, peas, water, and optional serrano peppers.
Bring to a boil; cover, reduce heat to low, and cook for 20 minutes.
Remove from heat; let rest for 5 minutes, then fluff with a fork.