Add the salt, black pepper, smoked paprika, cinnamon, ginger, thyme, cloves, and allspice to a small bowl and mix with a fork until well combined.
Wash your chicken, pat it dry with paper towels, and season both sides with the spice blend.
Heat one tablespoon of olive oil in a 12-inch cast-iron or heavy-bottomed skillet over medium-high heat. Cook the chicken thighs for 5 to 6 minutes on each side until cooked through to a temperature of 165°F. Transfer the chicken to a plate.
Melt the butter in the same skillet (do not wipe the skillet out!), add the apples and onions, and cook for 3 to 4 minutes until the onions begin to soften. Add the garlic and cook for another minute.
Add the brown sugar, maple syrup, and apple cider, and give everything a good stir with a wooden spoon. Lower the heat to medium and simmer the apples and sauce for 7 to 9 minutes, until the apples are tender but not mushy and the sauce has thickened slightly.
Add the chicken back to the skillet and spoon some of the sauce over the chicken. Remove the pan from the heat and garnish with fresh thyme leaves if desired.
Serve chicken thighs with apples and sauce spooned over top. Enjoy!