- Adjust oven rack to middle position and heat oven to 350 degrees. Process cilantro, 1/2 cup onion, Cubanelle, garlic, and cumin in food processor until finely chopped, about 20 seconds, scraping down bowl as needed. Transfer sofrito to bowl.
- Process mayonnaise, 1 1/2 tablespoons lemon juice, 1/8 teaspoon salt, and 2 tablespoons sofrito in now-empty processor until almost smooth, about 30 seconds. Transfer mayonnaise-herb sauce to small bowl, cover, and refrigerate until ready to serve.
- Pat chicken dry with paper towels and sprinkle with 1 teaspoon salt and 1/4 teaspoon pepper. Heat oil in Dutch oven over medium heat until shimmering. Add chicken to pot skin side down and cook without moving it until skin is crispy and golden, 7 to 9 minutes. Flip chicken and continue to cook until golden on second side, 7 to 9 minutes longer. Transfer chicken to plate; discard skin.
- Pour off all but 2 tablespoons fat from pot and heat over medium heat until shimmering. Add remaining 1/2 cup onion and cook until softened, 3 to 5 minutes. Stir in rice and Sazón and cook until edges of rice begin to turn translucent, about 2 minutes.
- Stir in broth, olives, capers, bay leaves, remaining sofrito, remaining 2 tablespoons lemon juice, 1 teaspoon salt, and 1/2 teaspoon pepper, scraping up any browned bits. Nestle chicken into pot along with any accumulated juices and bring to vigorous simmer. Cover, transfer to oven, and bake for 20 minutes.
- Transfer pot to wire rack and let stand, covered, for 15 minutes. Fluff rice with fork and stir in peas, if using. Discard bay leaves. Serve with mayonnaise-herb sauce and lemon wedges.
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