Heat oven to 400 degrees F. Line a baking sheet with foil for easy cleanup and spray with cooking spray.
Heat 2 tablespoons vegetable oil in a large cast-iron skillet over medium-high heat. Once the oil is very hot and just smoking, add the two pork tenderloins. You may need to work in batches. Sear each side of the pork until golden, then transfer to the foil lined baking sheet.
Bake at 400 degrees F until pork registers 145 degrees at the thickest part of the tenderloin, 15-20 minutes depending on thickness.
Transfer pork tenderloins to a cutting board. Let pork rest for 3-5 minutes before slicing. Brush slices with reserved sauce (that never touched the raw pork). Garnish with green onions if desired and season with freshly cracked salt and pepper to taste.