Slice the zucchini into ½-inch rounds and sprinkle with salt. Allow the zucchini to rest for about 15 minutes to draw out moisture.

In a large skillet, heat about 2 tablespoons of olive oil over medium heat. Add the diced onion and sauté for 2 minutes until it becomes translucent and fragrant.

Stir in the minced garlic and continue to cook for another 1–2 minutes until the garlic is golden but not burned.

Add the lean ground beef to the skillet. Cook for about 5 minutes, breaking it apart as you stir, until it’s no longer pink and begins to brown.

Drain any excess fat, then incorporate the drained diced tomatoes, Italian seasoning, kosher salt, and black pepper; mix well to combine and remove from heat.

Preheat your oven to 350°F (175°C). In an 8x8 baking dish, place half of the meat mixture on the bottom.

Add a layer of half the zucchini slices followed by half of the shredded mozzarella cheese. Repeat this layering process, finishing with the remaining cheese on top.

Place the baking dish in the preheated oven and bake uncovered for 20 to 25 minutes until the cheese is bubbly and golden brown on top.

After removing the casserole from the oven, let it rest for about 10 minutes before serving.