Set the Instant Pot to Sauté mode. Once hot, add olive oil and chopped onion. Sauté for 3–4 minutes until translucent. Add garlic and cook for another 30 seconds, stirring often.
Stir in rinsed rice and sauté for 2–3 minutes until lightly golden. Add cumin and salt. Mix well.
Press Cancel to stop sautéing. Stir in tomato sauce, chili powder if using, vegetable broth, and diced carrots. Scrape up any brown bits at the bottom of the pot to prevent a burn notice.
Secure the lid and set the Instant Pot to cook on Manual (High Pressure) for 4 minutes.
Allow the pressure to release naturally for 10 minutes, then quick release any remaining pressure.
Stir in the frozen peas immediately after opening the lid so they heat through but stay bright green. Fluff the rice with a fork.
Taste and adjust seasoning if needed. Serve with a squeeze of lime juice and garnish with fresh cilantro.
Notes
Refrigerator: Transfer leftover Mexican rice to an airtight container and refrigerate for up to 4 days.
Freezer: You can also freeze leftovers in an airtight container or freezer bag for up to 3 months. Thaw in the refrigerator before reheating.
To reheat: The best way to warm up leftovers is in the microwave, but you can also transfer them to a pan with a splash of broth, cover, and heat over medium-low until warned through.