Heat olive oil in the skillet over medium-low heat. Add onions, garlic, and sage, and sauté for 2-3 minutes.
Next, add in the flour and stir to combine.
Add in the almond milk and stir until a roux has started to form (the sauce will start to thicken), then add the yogurt, pumpkin puree, tomato paste, parmesan cheese, and salt and mix well. Add the vegetable broth and stir to combine.
Break the lasagna noodles into pieces (roughly into thirds) and immerse the noodles fully in the pumpkin sauce.
Cover the skillet and cook the noodles until they are al dente which takes approximately 20-25 minutes. While the noodles are cooking, gently scrape or stir the bottom of the pan every 5 minutes or so, so that the noodles don't stick to the bottom or burn.
Once the noodles are cooked through, sprinkle two handfuls of spinach on top of the lasagna. Then, sprinkle 2 cups of mozzarella cheese on top, followed by 8 dollops of ricotta cheese.
Cover the skillet again and let the cheese melt for a couple of minutes. Alternatively, you can broil the cheese to make it golden brown by putting the skillet in the broiler for a couple of minutes (be sure to remove the silicone handle on the skillet first, if there is one).
Notes
How to Store:Fridge. If you have leftover lasagna that you'll be eating soon, store it in the refrigerator in an air-tight container for up to 5 days.Freezing. If you have leftover lasagna that you want to save for another time, freezing it is a great option! Allow the lasagna to cool completely and then store it in a freezer-safe air-tight container for up to three months. I love freezing my lasagna in the 2-Cup Soupercubes Tray (their cubes are my favorite freeze-storage solution!).This is a great meal to make when you are in your third trimester of pregnancy so that you can have a delicious, no-effort home-cooked meal once the baby arrives.Reheating. To reheat your frozen lasagna, first, you will want to thaw it in the fridge overnight. Then, you can either reheat it quickly in the microwave for a few minutes until heated through, or you can reheat it in the oven by covering it with aluminum foil and baking it at 375 degrees Fahrenheit until heated through, about 45 minutes.