Preheat your oven to 400°F (200°C).

In a saucepan over medium heat, combine apple cider, brown sugar, garlic, salt, and pepper. Stir until the brown sugar has dissolved, then allow to simmer for about 10 minutes until the mixture thickens.

In an oven-safe skillet, heat a tablespoon of oil over high heat. Season the pork tenderloin with salt and pepper. Sear the pork for 2-3 minutes on each side until it is nicely browned.

Pour the apple cider glaze over the pork tenderloin and transfer the skillet to the oven. Bake for about 25-30 minutes, or until the internal temperature reaches 145°F (63°C).

While the pork cooks, place sweet potatoes in a pot and cover with water. Bring to a boil and cook until tender, about 15-20 minutes.

Drain and return sweet potatoes to the pot, then mash with butter, milk, cinnamon, and a pinch of salt.

Once the pork is done, let it rest for about 5 minutes before slicing. Serve with the sweet potato mash, drizzled with additional glaze for extra flavor.