01 -
Spray a 6- or 8-quart slow cooker with cooking spray. Place sliced onions evenly on the bottom.
02 -
Pat pork tenderloins dry with paper towels. Season all sides evenly with kosher salt and black pepper.
03 -
Heat olive oil in a large skillet over medium-high heat. Sear each pork tenderloin on all sides until browned, about 2-3 minutes per side. Transfer pork atop the onions in the slow cooker.
04 -
Pour low-sodium beef broth around the tenderloins, avoiding pouring directly on meat. Sprinkle pork gravy mix evenly over the top.
05 -
Place slices of butter on top of each tenderloin. Cover and cook on low for 2 to 2.5 hours, or until internal temperature reaches 145°F and onions are softened.
06 -
Remove tenderloins and slice. Serve immediately drizzled with the cooking juices as gravy.