Combine onion powder, garlic powder, paprika, salt and pepper and season both sides of the chicken breasts.
Mix together melted butter and buffalo sauce, then use two-thirds to brush both sides of the breasts (reserve the rest for later).
Preheat grill to medium and oil the grill grates, or heat an oiled grill pan on the stovetop.
Grill chicken for about 5–7 minutes per side, basting with hot sauce as it cooks, or until internal temperature reaches 165F / 74C.
When done, brush the remaining portion of the buffalo sauce over the chicken, and allow it to rest for a few minutes before slicing and serving.