In a bowl mix tomato paste, water, oregano, and garlic powder until well combined.
Lay 4 tortillas on a baking sheet. Sprinkle each with about 2 tbsp of vegan cheddar. Top each with the remaining tortillas.
Spread a thin layer of tomato sauce on top of each quesadilla. Set aside ⅓ if the spinach and sprinkle the remaining spinach evenly on each quesadilla. Top with parmesan cheese and bake for about 15 minutes until the edges if the tortilla are browned and crispy.
Remove from oven and top with remaining spinach, diced tomatoes, and avocado slices.
Slice each quesadilla pizza in quarters and enjoy.