Combine chicken, lemon juice, garlic, rosemary, oregano, fennel seeds and 2 tablespoons oil in a large zip-top plastic bag. Seal the bag; refrigerate for 25 to 30 minutes.

Remove the chicken from the marinade and pat dry (discard marinade). Sprinkle the chicken evenly with salt and pepper. Heat the remaining 1 tablespoon oil in a 10-inch cast-iron skillet over medium-high heat. Arrange the chicken, skin-side down, in the pan; cook, undisturbed, until browned and crispy, about 7 minutes. Flip and cook until browned on other side, about 4 minutes. Transfer to a plate. (The chicken will not be cooked through.) Do not wipe the pan clean.

Add onion and tomatoes to the pan; cook over medium-high heat, stirring occasionally, until the onion is charred and the tomatoes are blistered, about 5 minutes.

Preheat oven to broil with rack in center position. Add orzo and olives to the mixture in the skillet; stir to combine. Stir in broth. Bring to a boil over medium-high heat. Reduce heat to medium-low and nestle the chicken, skin-side up, into the mixture. Cover and simmer over medium-low heat until the orzo is al dente and a thermometer inserted into the thickest portion of chicken registers 165°F, 14 to 15 minutes.

Remove from heat; let stand, covered, for 5 minutes. Uncover and broil until the chicken skin is crisp, 2 to 3 minutes. Garnish with parsley, oregano and a squeeze of lemon juice, if desired. Serve immediately.