Preheat your oven to 375°F (190°C).
Bring a pot of salted water to a boil and cook the lasagna noodles until al dente, then drain and set aside.
Mince the garlic and roughly chop the fresh spinach.
In a skillet over medium heat, add the olive oil and sauté the garlic for 30 seconds until fragrant.
Add the ground beef to the skillet, seasoning with sea salt, black pepper, and dried oregano; cook until browned and crumbled.
Stir the tomato puree into the beef and simmer on low for 5 minutes to allow flavors to meld.
In a small mixing bowl, combine the ricotta cheese with the chopped spinach.
In a small individual-sized baking dish, spread a spoonful of meat sauce on the bottom.
Layer with half a noodle (cut to fit), half of the ricotta mixture, and a portion of the meat sauce.
Repeat the layers, finishing with the remaining meat sauce and a topping of shredded mozzarella cheese.
Bake for 20-25 minutes until the cheese is melted and the edges are bubbling.
Let the lasagna rest for 5 minutes before serving to allow the layers to set.