Heat a heavy-bottomed pot over medium heat. Add the olive oil to heat.
Once the oil is hot, add the onions. Cook until translucent, about 5 to 8 minutes.
Add the garlic and herbs and cook for another 2 minutes.
Add the tomato sauce and salt and pepper. Reduce the heat to low to maintain a simmer. Cook for 30 minutes while you prepare the rest of the lasagna. Note: The longer you let the sauce cook, the heavier and richer the flavor will be. A shorter cooking time will give a sweeter, fresher flavor.
Prepare the ricotta filling:
While the sauce is cooking, prepare the ricotta filling by placing the ricotta cheese, egg, salt, black pepper, and rosemary in a bowl. Mix all of the ingredients together until evenly blended. Set aside in the refrigerator.
Assemble the lasagna:
Preheat an oven to 375°F.
Spread a small layer of the sauce on the bottom of pan. Add 1 layer of fresh*, uncooked lasagna. Spread a thin layer of ricotta cheese on the pasta, topped with the eggplant slices, and mozzarella slices. Repeat this step 8 times until all of your ingredients have been used.*If you are using dried lasagna, you need to cook the lasagna first in boiling water according to the instructions.
Top the lasagna with a liberal drizzle of olive oil and a liberal sprinkling of salt and freshly ground black pepper.
Reduce the heat to 350°F, and bake the lasagna for 1 hour, or until it is bubbly.