4. Lay out the foil sheets on your counter. Divide the onions evenly among the centers of the foil, making a little bed of onions for each portion.
5. Place one piece of steak on top of each mound of onions. If any oil or seasoning is left in the onion bowl, spoon it over the steaks.
6. Fold each foil sheet up around the steak and onions: bring the long sides together over the top and fold them down tightly, then roll up the ends to make a sealed packet. Make sure there are no gaps so the steam stays inside and cooks everything gently.
7. Arrange the foil packets on a baking sheet in a single layer. Place the baking sheet in the preheated oven and bake for about 20–25 minutes for medium doneness, or a bit longer if you prefer your steak more well done or if you’re using a tougher cut.
8. Carefully remove the baking sheet from the oven and let the packets rest for 5 minutes. Use caution when opening them—the steam will be hot. Open each packet, spoon the soft onions and juices over the steak, and serve directly from the foil or transfer to plates.
Variations & Tips
For picky eaters, you can slice the steak into strips before cooking so it looks more like fajita meat and is easier for kids to cut and chew. If someone in the family isn’t a big fan of onions, simply use fewer onions in their packet or tuck the onions underneath so they flavor the meat without being front and center. For extra seasoning without adding more ingredients, use a coarsely ground seasoned salt instead of plain salt and pepper. You can also swap the olive oil for butter to make the dish a little richer, which my kids tend to love. To stretch the meal, add thinly sliced potatoes or carrots to the bottom of the packet under the onions—just keep the slices very thin so they cook through in the same time as the steak. If you’d like a bit of char, carefully open the packets at the end of baking and pop them under the broiler for 2–3 minutes, watching closely. Leftovers reheat nicely in the foil in a low oven, or you can slice the cold steak and onions and tuck them into sandwiches or wraps for an easy lunch the next day.
