01 -
Lightly spray a 6- or 8-quart slow cooker with cooking spray. Arrange the sliced onions evenly at the bottom of the cooker.
02 -
Pat pork tenderloins dry with paper towels. Season all sides generously with salt and freshly ground black pepper.
03 -
Heat olive oil in a large skillet over medium-high heat. Sear each tenderloin on all sides until evenly browned, about 2-3 minutes per side. Transfer seared tenderloins onto the bed of onions in the slow cooker.
04 -
Pour beef broth around the tenderloins in the slow cooker. Evenly sprinkle the pork gravy mix over the meat and onions.
05 -
Place sliced butter evenly on top of each tenderloin. Cover and cook on low for 2 to 2.5 hours, or until the internal temperature reaches 145°F and onions are soft.
06 -
Remove tenderloins and slice. Serve immediately with the cooking juices as gravy.