Set an Instant Pot to sauté on high. Meanwhile, pulse the onion, bell pepper, garlic and cilantro stems in a food processor until chopped into small pieces. When the pot is hot, add the olive oil, then add the chopped vegetables and season with salt. Cook, stirring occasionally, until the liquid is evaporated and the vegetables are soft, 6 to 8 minutes.
Stir in the chicken, rice, chicken broth, olives, Sazón seasoning, 3/4 teaspoon salt and a few grinds of pepper. Turn off the pot. Put on and lock the lid, making sure the steam valve is in the sealing position. Set the pot to pressure-cook on high for 5 minutes.
Meanwhile, put the peas in a small microwave-safe bowl. Microwave until heated through, about 1 minute.
When the time is up on the Instant Pot, let the pressure release naturally for 10 minutes, then carefully turn the steam valve to the venting position to release the remaining pressure. Turn off the pot and remove the lid. Fluff the rice and gently stir in the peas. Divide among bowls. Top with the cilantro leaves.