Season the Chicken: Season the chicken slices with salt and pepper according to your taste preferences.
Sauté Chicken: Set the Instant Pot to "Sauté" mode and heat olive oil. Add the seasoned chicken slices to the pot and cook until browned on both sides, about 3-4 minutes per side. Remove the chicken from the pot and set aside.
Sauté Aromatics: In the same pot, add minced garlic, diced onion, diced red bell pepper, diced carrot, peas, and optional celery and scallions. Sauté until the vegetables are softened, about 3-4 minutes.
Add Tomato Paste and Chicken Broth: Stir in the tomato paste until it's well incorporated with the vegetables. Pour in the chicken broth and stir to combine, scraping any browned bits from the bottom of the pot.
Add Rice and Chicken: Add the uncooked white rice to the pot and stir to combine with the vegetable mixture. Return the browned chicken slices to the pot and nestle them into the rice mixture.
Pressure Cook: Close the Instant Pot lid. Set the Instant Pot to "Manual" or "Pressure Cook" mode on high pressure for 8 minutes.
Natural Release: Once the cooking cycle is complete, allow the pressure to release naturally for 10 minutes before performing a quick release.
Serve: Open the lid carefully and stir the chicken, rice, and vegetable mixture. Serve the Chicken Cuban Rice hot, garnished with chopped scallions or fresh cilantro, if desired. Enjoy!
Note: Storage: Leftovers can be stored in an airtight container in the refrigerator for up to 3 days.