This vegetable lasagna is perfect for making ahead and can easily transport to a potluck or the freezer.
Preheat oven to 375º.
Heat oil in a medium saucepan over medium heat. Add mushrooms and the next 4 ingredients (mushrooms through onion); cook for 5 minutes, stirring frequently. Add pasta sauce; bring to a boil. Reduce heat, and simmer 10 minutes.
Combine pesto and ricotta in a small bowl. Spread 1/2 cup tomato mixture in the bottom of a 8-inch square baking dish or pan coated with cooking spray. Arrange 4 noodle halves over tomato mixture. Top noodles with half of ricotta mixture and 1 cup tomato mixture. Repeat layers, ending with noodles. Spread remaining tomato mixture over noodles; sprinkle with mozzarella.
Cover and bake at 375º for 30 minutes. Uncover and bake an additional 20 minutes. Let stand 10 minutes.
Notes: To make ahead, assemble as directed; stop before baking. Cover and refrigerate overnight. Let stand 30 minutes at room temperature; bake as directed. For easy cleanup, assemble in a disposable 8-inch aluminum-foil pan. If you're making for a gift, deliver uncooked with baking instructions.