Preheat your oven to 375°F (190°C).
Boil the whole wheat lasagna noodles in a pot of salted water according to package directions until al dente, then drain and set aside.
In a non-stick skillet over medium heat, sauté the diced yellow onion and minced garlic until they become soft and translucent.
Add the ground beef to the skillet, seasoning with half of the sea salt and black pepper, and cook until fully browned; drain any excess fat from the pan.
In a small mixing bowl, lightly whisk the egg and then stir in the ricotta cheese, dried oregano, and the remaining salt and pepper until well combined.
Spread a thin layer of marinara sauce on the bottom of a small individual-sized baking dish.
Layer one noodle (cut or folded to fit the dish), half of the cooked beef mixture, half of the ricotta mixture, and a spoonful of marinara sauce.
Repeat the layers with the second noodle, the remaining beef, the remaining ricotta, and the rest of the sauce.
Top the final layer with the shredded mozzarella cheese and cover the dish tightly with foil.
Bake for 20 minutes, then remove the foil and bake for an additional 10 minutes until the cheese is bubbly and golden brown.
Let the lasagna rest for 5 minutes before garnishing with fresh torn basil leaves and serving.