Preheat your oven to 375°F and prepare a small individual-sized baking dish.
Cook the whole wheat lasagna noodles in boiling water until al dente, then drain and set aside.
In a skillet over medium heat, add the olive oil and sauté the diced onion and minced garlic until translucent.
Add the ground beef to the skillet, browning it completely while breaking it into small crumbles.
Stir in the tomato puree, dried oregano, sea salt, and black pepper, then simmer for 5 minutes.
In a small bowl, combine the ricotta cheese, whisked egg, and chopped fresh spinach until well mixed.
Spread a spoonful of the meat sauce on the bottom of the baking dish, followed by a portion of the lasagna noodle trimmed to fit.
Layer half of the ricotta mixture over the noodle, followed by more meat sauce and the remaining noodle pieces.
Top with the remaining meat sauce, shredded mozzarella, and grated parmesan cheese.
Bake for 20-25 minutes until the cheese is bubbly and the edges are golden brown.