Preheat the oven to 400Place a 13×9.x2 inch baking sheet on top of a rimmed baking sheet.
Heat 1 tablespoon olive oil in a large saucepan over medium-high heat. Add the turkey, garlic, oregano, red pepper, and 1/2 teaspoon salt and cook, stirring frequently, until the turkey is lightly browned, about 5 minutes. Add the marinara sauce and simmer over low heat while preparing the remaining ingredients.
In a large skillet, heat the remaining 1 tablespoon oil over medium heat, and cook the spinach with the remaining 1/2 teaspoon salt until wilted, about 3 minutes.
In a medium bowl, combine the sweet potato, ricotta, eggs and black pepper.
In the bottom of the baking dish, spread 1 1/2 cups of the meat sauce, and top with a layer of 5 noodles. Spread half the sweet potato mixture over the noodles and top with all of the spinach. Start another layer with 1 1/2 cups of the sauce, then half the shredded mozzarella, 5 noodles, and the remaining sweet potato mixture. Top with another 1 1/2 cups sauce, the remaining shredded mozzarella, and finally the parmesan.
Cover the dish with foil. Bake in the center of the oven on top of the baking sheet (to catch any drippingfor 25-30 minutes. If you made the meat sauce and sweet potatoes in advance and they were added cold, bake an extra 15 minutes.
Remove the foil and bake until golden and bubbling, 10-15 minutes. Cool for 15 minutes prior to serving and slicing.
Notes
Adapted from Run Fast. Eat Slow. By: Shalane Flanagan & Elyse KopeckyI like to line a cookie sheet with foil and bake sweet potatoes at 425 until cooked and soft. It depends on how big they are. It can take anywhere from 40 minutes to 1 hour. Also optiona to peel and boil the sweet potatoes.