Pollo Asado (Mexican Grilled Chicken)

In a large skillet, heat oil over medium-high heat until shimmering. Add garlic and chiles. Cook, flipping occasionally, until charred in spots, about 4 minutes. Transfer to a blender. Add onion petals to now-empty skillet in an even layer and cook over medium-high heat, flipping once, until charred on both sides, 3 minutes. Add to blender along with oregano, coriander, cumin, kosher salt, and black pepper. Blend until smooth. You should have about 2 cups marinade total. Reserve 1/2 cup of marinade in a separate bowl and set that aside.

In a large bowl, combine cut chicken pieces with the remaining marinade (about 1 1/2 cups). Refrigerate, covered, for at least 1 hour and up to 12 hours.

Meanwhile, in a small saucepan, add reserved chicken spine, wing tips, and trimmings, along with 1/2 cup water, and cook, covered, over low heat until fat is rendered, 45 to 60 minutes. Strain and discard solids. Return liquid to pot over medium heat. Add the reserved 1/2 cup marinade to the strained liquid in pot, and stir to combine. Set prepared chicken sauce aside.

For a Charcoal Grill: Open bottom vent completely. Light large chimney starter, 3/4-filled with charcoal briquettes (4 quarts). When top coals are partially covered with ash, pour evenly over grill grate. Set cooking grate in place, cover, and open lid vent completely. Heat grill until hot, about 5 minutes. For a Gas Grill: Turn all burners to high, cover, and heat grill until hot, about 15 minutes. Lower burners to medium heat.

Clean and oil the cooking grate. Place chicken pieces, skin-side down, on the grill and cook, covered, moving and flipping the chicken as needed to avoid scorching, until the white meat registers 155°F (68℃) and the dark meat registers at least 175°F (80℃) with a digital thermometer, 15 to 35 minutes depending on the cut. Transfer chicken to a large plate or rimmed baking sheet as it finishes cooking.

Squeeze lime halves over chicken and brush all over with prepared chicken sauce. Serve with rice, beans, and warm tortillas.