Preheat oven to 375 Fahrenheit.
In a pan, cook turkey sausage over medium heat until browned and set aside.
In a large casserole dish, spread quinoa on the bottom and then top with cooked sausage and diced vegetables.
In a large mixing glass, stir together marinara, tomato paste, broth, and seasoning and pour over chopped vegetables.
Stir liquid and quinoa mixture to make sure evenly distributed.
Cover with foil and bake for 45 minutes.
Remove foil, stir again, and bake for 10 more minutes or until quinoa has absorbed liquid.
Cover casserole with the shredded cheese and bake for about 4 minutes or until cheese is melted.
Top with pepperoni slices and serve!