Preheat your oven to 400°F (200°C).
Season the pork tenderloin generously with salt and pepper.
In a large ovenproof skillet, heat olive oil over medium-high heat.
Add the pork tenderloin to the skillet and sear on all sides until golden brown, about 2-3 minutes per side.
Remove the pork from the skillet and set aside.
In the same skillet, add the sliced onions and cook until softened, about 5 minutes.
Add the sliced apples and fresh sage to the skillet; cook for an additional 3-4 minutes until the apples begin to soften.
Return the pork tenderloin to the skillet, nestling it among the onions and apples.
Pour the chicken broth around the pork, then transfer the skillet to the preheated oven.
Roast in the oven for 25-30 minutes, or until the pork reaches an internal temperature of 145°F (63°C).
Remove the skillet from the oven and let the pork rest for 5-10 minutes before slicing.
Slice the pork and serve it with the apples and onions, drizzled with the pan sauce.