Preheat oven to 375°F Cook lasagna noodles according to package directions. Drain lasagna noodles; rinse with cold water and drain well. Lay lasagna noodles in a single layer on a sheet of foil.
In a medium bowl, combine egg, ricotta cheese, 1 cup of the mozzarella, 1/4 teaspoon salt and 1/4 teaspoon black pepper; set aside.
To assemble pie, lightly coat a 9-inch sprinform pan with nonstick cooking spray. Arrange four of the lasagna noodles in the bottom of the pan, trimming and overlapping as necessary to cover bottom of pan with one layer of noodles. Top with spinach. Spoon half of the ricotta cheese mixture over spinach, spreading evenly. Spoon one-third of the pesto over ricotta layer, spreading evenly. Top with another layer of lasagna noodles, trimming to fit. Top with mushrooms. Spread remaining ricotta cheese mixture over mushrooms. Spread half of the remaining pesto over ricotta layer. Top with another layer of lasagna noodles and remaining pesto. Top with tomatoes.
Place sprinform pan in a foil-lined shallow baking pan. Bake, covered, for 45 minutes. Uncover and sprinkle with remaining 1 cup of cheese. Bake, uncovered, for about 15 minutes more or until cheese is melted and lasagna is heated through. Cover and let stand on a wire rack for 20 minutes before serving. Carefully remove side of springform pan.