I've made this spinach lasagna several times and really love the kick from the lemon.
adapted from Food Network
salt and freshly ground black pepper
9 dry lasagna noodles
1/4 cup extra-virgin olive oil
2 cloves garlic, minced
1 (10-ounce) box frozen spinach, thawed and drained
1 pound ricotta cheese (about 1 3/4 cups)
3/4 cup freshly grated Parmesan, Pecorino Romano, or a combination
1 pound fresh mozzarella, shredded (about 4 cups)
Finely grated zest of 1 small lemon
1/2 teaspoon freshly grated nutmeg
1/8 teaspoon cayenne
1 large egg, beaten
4 cups marinara sauce
Preheat the oven to 350 degrees F.
Bring a large pot of water to a boil over high heat and salt it generously. Add the lasagna noodles and boil, stirring occasionally, until al dente, about 8 to 10 minutes. Drain.
Meanwhile, heat the olive oil and garlic in a saucepan over medium heat until the garlic begins to brown. Add the spinach, season with salt and pepper and stir until the spinach dries out and the garlic is fragrant, about 3 minutes. Cool.
Mix ricotta cheese, Parmesan/Pecorino, 2 cups of the mozzarella cheese, lemon zest, nutmeg, cayenne, and egg in a bowl. Add cooled spinach to the bowl. Season with salt and pepper, to taste.
Cover the bottom of a 9 by 13-inch casserole with a thin layer of tomato sauce. Cover with 3 noodles placed side-to-side, but not overlapping. Top with a 1/3 of the cheese mixture and a third of tomato sauce. Season lightly with salt and pepper. Repeat to make one more layers. Cover lasagna layers with remaining noodles. Drizzle with remaining tomato sauce, then scatter the remaining 2 cups mozzarella on top. Bake, uncovered, until the lasagna is hot and bubbly, about 40 to 45 minutes. Let lasagna stand for 10 minutes before serving.