Instructions
Step 1: Prepare Oven and Foil
Heat the oven to 400°F. Tear off four large sheets of heavy-duty foil, making sure each piece is large enough to loosely wrap the steak and onions while sealing in moisture.
Step 2: Season the Onions
In a bowl, toss the sliced onions with the olive oil (or melted butter) and half of the salt and pepper until evenly coated.
Step 3: Season the Steak
Divide the steak into four portions. Pat dry with paper towels, then season both sides with the remaining salt and pepper.
Step 4: Assemble the Foil Packets
Place a layer of seasoned onions in the center of each foil sheet. Set a steak portion on top and drizzle any remaining oil or butter over the meat.
Step 5: Seal and Bake
Fold the foil over the contents and crimp the edges tightly to form sealed packets. Arrange the packets on a baking sheet and bake for 20–25 minutes, depending on thickness, for medium doneness.
Step 6: Rest and Serve
Remove from the oven and let the packets rest, unopened, for 5 minutes. Carefully open to release the steam, then spoon the tender onions and cooking juices over the steak before serving.
