Preheat the oven to 375 degrees. Pat the pork tenderloin dry and set aside.
Preheat an oven-safe skillet over medium to medium-high heat.
Meanwhile, combine the spice rub ingredients in a small bowl. Mix together. Spread out on a meat-safe cutting board (or on a piece of parchment paper). Roll the pork in the spice mixture to coat evenly on all sides.
Add the oil to the skillet and add the tenderloin. Sear for 3-4 minutes until browned. Flip and cook on the second side for 1-2 minutes.
Transfer the skillet to the oven and cook for 15-20 minutes or until the internal temperature reaches 145 degrees for medium-rare or 160 degrees for medium. The cooking time will vary depending on the thickness of the tenderloin.
Let the pork rest for 5 minutes before slicing.
While the pork roasts in the oven, preheat a skillet over medium heat and melt the butter. Add the apples and onions and season with the ground cloves. Cook until the onions are lightly brown and the apples are slightly softened but still firm.
Slice the pork and serve family-style alongside the apples and onions. Garnish with fresh thyme.