1 (3 1/2 to 4 pound) chicken, cut into parts (alternatively, 3 to 3 1/2 pounds of bone-in, skin-on chicken parts, such as breasts, thighs and legs)
Kosher salt and freshly ground pepper
1 ½ cups full-fat Greek yogurt, divided
5 tablespoons fresh lemon juice, divided
2 teaspoons ground turmeric, divided
2 (15-ounce) cans chickpeas, drained and rinsed
1 tablespoon fennel seed
1 teaspoon ground cumin
1 large red onion, thinly sliced, divided
2 tablespoons olive oil
½ cup mint or cilantro leaves, torn
Season chicken parts with salt and pepper.Combine 3/4 cup yogurt, 2 tablespoons lemon juice, 1 teaspoon turmeric and 2 tablespoons water in a large bowl. Season well with salt and pepper. (It should be on the salty side, as this is a marinade.) Add chicken and toss to coat evenly. Let sit at least 30 minutes at room temperature, and up to overnight in the refrigerator.
Place oven rack on the top third of the oven and heat to 425 degrees. Combine chickpeas, fennel seed, cumin, remaining teaspoon of turmeric and half the red onion slices on a rimmed baking sheet. Drizzle with olive oil, season with salt and pepper and toss to coat. Move chickpeas to the outer edges of the baking sheet. Scrape any excess marinade off the chicken, and place the chicken parts in the center. Place baking sheet in oven and bake, tossing chickpeas occasionally, until the skin of the chicken is evenly browned and the chickpeas are golden and starting to crisp, 45 to 50 minutes.
Meanwhile, toss remaining onion slices with 2 tablespoons lemon juice and season with salt and pepper; set aside.Combine remaining yogurt with remaining 1 tablespoon lemon juice and season with salt and pepper; set aside.Once chicken is ready, scatter with lemony onions and mint or cilantro.
Serve with seasoned yogurt alongside as a sauce.