Heat the oven to 425°F with a rack in the middle. Line a large rimmed sheet pan with parchment paper or foil for easier cleanup.

Put the chickpeas in a colander, rinse them under cold water, and let them drain well. Spread them on a clean towel or paper towels and pat them as dry as you can so they roast instead of steam.

Cut the bell peppers into 1-inch strips and cut the red onion into 1/2-inch wedges. Pull apart any onion layers that are stuck tightly together.

Zest the lemon into a large bowl. Cut the lemon in half and squeeze in 2 tablespoons of juice.

Add the garlic, olive oil, smoked paprika, cumin, kosher salt, and black pepper to the bowl with the lemon. Stir until the seasonings are evenly mixed.

Pat the chicken thighs dry with paper towels. Put the chicken into the bowl and turn it in the seasoning mixture until all of the pieces are coated.

Lift the chicken out of the bowl and set it on a plate for a moment. Keep the remaining seasoning mixture in the bowl.

Put the chickpeas, bell peppers, and red onion into the same bowl. Toss well so the vegetables and chickpeas are coated with the remaining seasoned oil.

Transfer the chickpea and vegetable mixture to the sheet pan. Spread everything into one even layer so the hot air can reach the food.

Set the chicken thighs on top of the vegetables and chickpeas, leaving a little space between the pieces. Scrape any seasoning left in the bowl over the chicken.

Put the sheet pan in the oven and roast for 20 minutes. The chicken will start to firm up and the vegetables will begin to soften.

Pull the sheet pan out of the oven and set it on the stove. Use a spatula to turn the chickpeas and vegetables so they brown more evenly, moving any chickpeas trapped under the chicken into the open parts of the pan.