In a bowl, mix together the ground beef with plenty of salt and pepper. Separate the ground beef evenly and press into four patties.
Heat olive oil in a cast iron skillet or grill pan (or use your grill) over medium-high heat and add the patties.
Cook for approximately 7-8 minutes on both sides until it reaches your desired doneness (at least 155 F). Set them aside on a paper towel to drain briefly. Turn off the pan.
Line four meal prep containers with lettuce leaves and transfer the patties to the containers. Top each patty with mayo, and add the tomato and onion slices.
Seal the containers and refrigerate until ready to use. When it's time to eat, serve with your favorite veggie chips or carrot sticks, and enjoy!
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Notes
You can also add cheese slices if you prefer. This recipe makes four meals. Macros are not calculated for the chips and cheese.