In a small bowl whisk the marinade ingredients. Place the chicken in a large resealable plastic bag and pour in the marinade. Press the air out of the bag and seal tightly. Turn the bag to distribute the marinade, place in a bowl, and refrigerate for 2 to 4 hours.
Prepare the grill for direct and indirect cooking over medium heat (350° to 450°F) and preheat a 12-inch cast-iron skillet over indirect heat for 10 minutes.
Add the oil and tomatoes to the cast-iron skillet and stir to coat. Cook over indirect medium heat, with the lid closed, until the tomatoes begin to break down, 10 to 12 minutes, stirring occasionally. Add the chickpeas, cumin, garlic, salt, and red pepper flakes and stir to combine. Continue to cook, with the lid closed, until the tomatoes release their juices and the sauce is slightly thickened, about 15 minutes, stirring occasionally. During the last minute of cooking the tomatoes, add the cilantro.
While the tomatoes are cooking, grill the chicken. Remove the chicken from the bag and discard the marinade. Grill the chicken, skin side down first, over direct medium heat, with the lid closed, until the meat is firm to the touch and opaque all the way to the center, 8 to 12 minutes, turning once. Remove from the grill and let rest for 3 to 5 minutes.
Serve the chicken warm with the tomato mixture spooned over the top.