First, preheat the oven to 400ºF.

Prepare pork tenderloin. Place spices into a small bowl and mix to combine. Then, gently pat pork tenderloin with the spice rub, covering the pork entirely.

Heat 3 tablespoons of butter in a large cast-iron skillet over medium/high heat. When the butter is melted and fragrant, sear pork tenderloin for 2-3 minutes on each side.

Remove pork tenderloin from cast iron and turn the heat down to low/medium. Deglaze the pan with 1.5 cups broth and use a wooden utensil to scrape the brown bits from the bottom.

Then, add onion, garlic, mushrooms, and balsamic vinegar. Let cook for 3 minutes.

Turn heat off, place the pork tenderloin back into the cast iron skillet, moving the veggies aside so that they're surrounding the pork.

Roast at 400ºF for 10 minutes. Remove from the oven, check the temperature, flip the pork tenderloin over, and bake for an additional 12-16 more minutes or until the internal temperature of the thickest part reaches 145ºF.

Once the temperature has reached 145ºF, remove the pork tenderloin from the oven and set aside on a large plate to rest.