Heat butter in a skillet over medium heat until melted.
Add minced red onions and cook until aromatic, about 2 minutes.
Stir in chopped parsley and garlic, then pour in fresh lemon juice followed by red pepper flakes.
Pour in chicken stock, then add Parmesan cheese and stir to combine.
Mix in heavy whipping cream and let the sauce simmer gently for 1 minute before removing from heat to cool slightly.
Season the chicken pieces with kosher salt, smoked paprika, and chicken seasoning; toss to evenly coat.
Place the chicken in a baking dish and spoon the prepared sauce over it.
Bake uncovered at 375°F (190°C) for 1 hour and 45 minutes, turning the chicken over halfway through cooking.
Finish by placing the chicken under the broiler skin-side up until the skin turns golden brown.
Baste the chicken with the sauce before serving and enjoy!