Step 1: Prepare the zucchini: Slice zucchini lengthwise into 1/8 to 1/4-inch thick strips using a mandoline or sharp knife. Lay slices in a single layer on paper towels, sprinkle with 1 teaspoon of salt, and let sit for 30 minutes to draw out moisture. Gently blot thoroughly with more paper towels to remove excess liquid.
Step 2: Make the meat sauce: Heat olive oil in a large skillet or Dutch oven over medium-high heat. Add ground beef and cook, breaking it apart with a spoon, until browned. Drain any excess fat. Add diced onion and minced garlic; cook until softened and fragrant, about 5-7 minutes.
Step 3: Finish the sauce: Stir in crushed tomatoes, tomato paste, dried oregano, dried basil, and red pepper flakes (if using). Season with salt and black pepper. Bring to a simmer, then reduce heat to low, cover, and cook for at least 20-30 minutes, stirring occasionally, to allow flavors to meld.
Step 4: Prepare the cheese filling: In a medium bowl, combine ricotta cheese, 1/2 cup Parmesan cheese, chopped parsley, and egg. Mix well until smooth and thoroughly combined. Season with a pinch of salt and black pepper.
Step 5: Assemble the lasagna: Preheat oven to 375°F (190°C). Lightly grease a 9x13-inch baking dish. Spread a thin layer of meat sauce on the bottom of the dish. Arrange a single layer of dried zucchini slices over the sauce, overlapping slightly. Spread half of the ricotta cheese mixture evenly over the zucchini. Sprinkle with about one-third of the shredded mozzarella cheese.
Step 6: Continue layering: Top with another layer of meat sauce. Repeat the zucchini, ricotta, mozzarella, and meat sauce layers. Finish with a final layer of zucchini slices, topped generously with the remaining mozzarella and a sprinkle of additional Parmesan cheese.
Step 7: Bake: Cover the baking dish loosely with aluminum foil. Bake for 30 minutes. Remove the foil and continue baking for another 15-20 minutes, or until the cheese is melted, bubbly, and lightly golden brown. If desired, broil for 1-2 minutes for extra browning (watch carefully!).
Step 8: Rest and serve: Let the lasagna rest for 10-15 minutes before slicing and serving. This allows the layers to set and makes for cleaner slices. Enjoy your delicious low-carb zucchini lasagna!