In a small bowl, combine the chili pepper flakes, ginger, garlic, soy sauce, honey, and lemon zest.
Place the chicken pieces in a bowl and pour the marinade over the chicken gently toss to coat.
Refrigerate for at least 6-8 hours or overnight.
Preheat the oven and a baking sheet to 400°F.
Place the chicken thighs skin side up on the preheated baking sheet arranging in a single layer with room between the pieces. Add the onion quarters and arrange the lemon slices in between the pieces of chicken.
Bake the chicken for 25 minutes, remove the baking pan from the oven and flip the chicken over. Spoon drippings over the chicken.
Reduce the oven to 375 degrees and return the chicken to the oven for 15 minutes.
Flip the chicken over again to skin side up and cook until the skin is crispy and internal temperature reached 165 degrees or higher, about another 15- 20 minutes.
Remove chicken and let rest for 5 minutes.
Plate and drizzle the drippings over the chicken and arrange the onions and lemons on the serving platter.
Serve with your favorite sides.