Preheat oven to 400°F (200°C) and pat pork tenderloins dry.
Mix brown sugar, lemon pepper, smoked paprika, garlic powder, onion powder, lemon juice, and olive oil to form a paste.
Rub the mixture evenly over all pork sides.
Heat an oven-safe skillet over medium-high heat and add olive oil if needed.
Sear pork tenderloins on all sides until golden brown, about 2–3 minutes per side.
Transfer skillet to the oven and roast pork for 18–25 minutes until internal temperature reaches 145°F (63°C).
Remove pork from oven and let rest for 5–10 minutes before slicing.
Prepare chimichurri sauce by pulsing green onions, parsley, cilantro, and garlic in a food processor until finely chopped.
Add apple cider vinegar, lemon juice, lemon zest, salt, and pepper to the processor.
Slowly drizzle in olive oil while processing until combined but slightly textured.
Adjust seasoning to taste.
Slice pork into medallions and spoon chimichurri sauce over the top.
Serve immediately.