Preheat your oven to 425°F (220°C).
Generously season the bone-in chicken thighs with onion powder, garlic powder, smoked paprika, fresh thyme, salt, pepper, and chopped rosemary.
In an oven-safe skillet over medium-high heat, add olive oil and sear the seasoned chicken thighs on both sides until they are golden brown—about 5-7 minutes per side.
Once seared, surround the chicken in the skillet with sliced red onion and honeycrisp apples.
Transfer your skillet to the preheated oven and bake for about 20-25 minutes or until the internal temperature of the chicken reaches 165°F (75°C).
After removing chicken and apples from the pan, place it back on medium heat on your stovetop. Add salted butter, apple cider, chicken broth (or white grape juice), Dijon mustard, and minced garlic into the hot skillet.
Whisk together until combined and cook until thickened slightly—about 5 minutes should suffice. Return your chicken and apples back into the pan allowing them to absorb some of that delicious sauce before serving hot!