The best thing about Meatless Mondays is the versatility and inventiveness that each recipe brings. With the Vegetarian Tortilla Casserole (pictured above), your typical, run-of-the-mill casserole is turned on its head as this recipe features two unlikely ingredients: salsa verde and squash. This gives the meal some unexpected, spicy fall flair. Those two mainstays are accompanied by mozzarella and Parmesan cheeses, corn tortillas, scallions and tomato to make for a perfectly tangy meal. And it's gluten-free to boot.

This meal is relatively simple to make. First, you'll season the cut-up squash with salt and bake till it's soft. Then, you'll combine the mozzarella and Parmesan cheeses and salt in a bowl.

Once that's completed, place and overlap 4 tortillas in a baking dish and place the squash and scallions on top. Then, drizzle the salsa verde over the vegetables and top with the cheese mixture. Again, place and overlap 4 tortillas on top. Then, put the sliced tomatoes and spinach over it, and cover with the salsa verde and cheese mixture. Place 4 tortillas on top and pour the last of the salsa verde and cheese mixture over it. Bake until golden brown. Add the leftover scallions to garnish.

Meatless Monday, an international movement, encourages people everywhere to cut meat one day a week for personal and planetary health. Browse more Meatless Monday recipes.