Preheat your oven to 400°F (200°C).
Wash the potato and slice it into very thin rounds, approximately 1/8-inch thick, and set aside.
In a large oven-safe skillet or pan over medium-high heat, add the olive oil and sauté the diced onion, bell pepper, and zucchini for 5 minutes until softened.
Add the ground beef and minced garlic to the skillet, breaking the meat up with a wooden spoon until it is fully browned.
Stir in the tomato puree, sea salt, black pepper, and dried oregano, allowing the mixture to simmer for 2 minutes to meld the flavors.
If using a separate baking dish, transfer the beef and vegetable mixture now, spreading it into an even layer.
Arrange the potato slices on top of the beef mixture in an overlapping shingle pattern, then sprinkle evenly with the grated parmesan cheese.
Cover the dish tightly with foil and bake for 20 minutes.
Remove the foil and bake for an additional 10-15 minutes until the potatoes are fork-tender and the cheese has turned golden brown.