Preheat the oven to 375°F. Sprinkle the sliced eggplant with salt and let it sit for 30 minutes to draw out moisture. Rinse and pat dry with paper towels.

In a large skillet, heat olive oil over medium heat. Add the ground beef or turkey, onion, and garlic. Cook until the meat is browned and the onion is translucent, about 5-7 minutes. Drain excess fat if necessary.

Stir in the crushed tomatoes, oregano, basil, black pepper, and red pepper flakes. Simmer for 10 minutes, then remove from heat.

In a bowl, combine ricotta cheese, egg, and a pinch of salt. Mix until smooth.

In a 9x13-inch baking dish, spread a thin layer of the meat sauce on the bottom. Layer half of the eggplant slices over the sauce, followed by half of the ricotta mixture, half of the mozzarella, and a third of the remaining meat sauce. Repeat the layers, finishing with the remaining meat sauce and topping with Parmesan cheese.

Cover the dish with aluminum foil and bake for 30 minutes. Remove the foil and bake for an additional 15 minutes, or until the cheese is bubbly and golden.

Allow the lasagna to cool for 10 minutes before slicing and serving.