Heat the olive oil in a large skillet over medium-high heat. Add the ground beef and diced onion. Cook, breaking up the beef as it browns, until no longer pink. Drain any excess grease.

Season the beef with 1 teaspoon of the salt and the black pepper. Stir in the minced garlic and cook for 1 minute.

Add the crushed tomatoes and fresh basil. Reduce the heat to low, cover, and simmer for 20–30 minutes, or until the sauce has thickened.

Meanwhile, slice the zucchini lengthwise into approximately ?-inch-thick slices. Arrange the slices on paper towels and sprinkle with the remaining 1 teaspoon salt.

Let the zucchini sit for 10–15 minutes, then blot well with paper towels to remove excess moisture.

In a medium bowl, stir together the ricotta cheese, shredded Parmesan, and egg until combined.

Preheat the oven to 400°F.

Spread about ½ cup of the meat sauce evenly over the bottom of a 9x13-inch baking dish. Arrange a single layer of zucchini slices over the sauce.

Spread half of the remaining meat sauce over the zucchini. Top with half of the ricotta mixture and 1 cup of the mozzarella cheese.

Repeat with another layer of zucchini, the remaining meat sauce, the remaining ricotta mixture, and 1 cup of mozzarella.

Top with a final layer of zucchini and cover the baking dish with foil.

Bake for 30 minutes. Remove the foil and bake for another 10 minutes, or until the zucchini is tender and the sauce has thickened.

Sprinkle the remaining 1 cup mozzarella cheese over the top. Bake uncovered for 5 minutes, or until the cheese is melted.

Remove from the oven and let the lasagna rest for 10–15 minutes before slicing and serving.