The sweetness of butternut squash and roasted onions and garlic are the perfect complement to ground beef and fresh herbs, so why not give your lasagna a seasonal twist? This recipe calls for roasted butternut squash, but if you have leftover baked sweet potatoes on hand, you can use them instead.
Heat the oven to 400 degrees.
Brush the squash lightly with olive oil, sprinkle it with salt, and place it cut-side-down on a sheet pan. Roast it in the oven for 15 minutes. Add the onion and garlic to the pan, brush them with oil, and sprinkle them with salt; continue roasting the vegetables until soft and slightly charred. Remove the pan from the oven, reduce the oven temperature to 375 degrees, and then allow the squash to cool slightly before removing the skin.
Place the roasted squash, onion, and garlic into the bowl of a food processor with 4 tablespoons olive oil and salt to taste. Purée until smooth. Set aside.
Brown the ground beef, season with salt, and then set aside.
Spray an 8-inch square baking dish with non-stick cooking spray. Pour a small amount of marinara sauce in the bottom. Lay two oven-ready lasagna noodles in the bottom and top with the ground beef.
Spread a thin layer of marinara sauce over the ground beef and then add two more sheets of pasta.
Spread the butternut squash purée over the top, sprinkle it with fresh thyme and salt to taste, and then add another two sheets of pasta.
Spread the ricotta cheese over the pasta, add the last two sheets of pasta, and top with marinara sauce.
Cover the lasagna with foil and bake for 20 minutes. Then, remove the foil, top with the grated Parmigiano-Reggiano, and bake for another 10 minutes or until the cheese is melted.
Let the lasagna cool for 10 minutes before serving.