Preheat your oven to 350 degrees Fahrenheit.

Heat oil over medium heat in your big skillet. Add the bell peppers and the onion and cook until tender. Put the ground beef and cook for 2 minutes before adding the zucchini, mushrooms, and garlic. Cook for another two minutes, making sure everything is stirred through. Add the remaining marinara sauce, lower the heat and simmer for about 10 minutes.

Use about half a cup of marinara sauce to line the bottom of a baking dish. Lay 9 slices of your sun-dried polenta over the marinara sauce.

Once the mixture has done simmering for 10 minutes, add half of the batch on top of the polenta. Spread half of your cheese over the top. Lay the remaining nine slices of polenta over the cheese, add the rest of the beef and vegetables and cover with the remaining cheese.

Cover and bake for around half an hour. Take the lid off and cook for another 15 minutes until the cheese is nice and bubbly.

If you like your lasagna a little more cheesy, feel free to add some more in (low fat, of course). You can also experiment with the sort of vegetables you include. I know some people aren't keen on zucchini, so that you can replace this with something like eggplant or even sweet potato would work well.