Persian Chicken Kebabs

1.In a medium bowl, combine the yogurt, olive oil, paprika, cumin, cinnamon, red pepper flakes, lemon zest, lemon juice, salt, pepper and garlic. Add chicken and mix well. Refrigerate overnight.
2.Thread the chicken onto skewers, folding if the pieces are long and thin, alternating occasionally with the onion. Be sure not to cram the skewers.
3.Preheat the grill to medium-high heat. To grease the grill, lightly dip a wad of paper towels in vegetable oil and, using tongs, carefully rub over the grates several times until glossy and coated. Grill the chicken kebabs until golden brown and cooked through, turning skewers occasionally, 10 to 15 minutes. If broiling, place kebabs on sheet pan with a rack, turn broiler on high and broil 8 minutes per side.