1. Preheat oven to 350 degrees Fahrenheit. Heat olive oil in a medium sized pot and saute onion, bell pepper, zucchini and garlic until they are soft. Stir in the cumin, taco seasoning, and oregano and then add the drained tomatoes (reserve juice) and spinach.
2. Add the black beans, water and quinoa. Bring to a boil and then lower heat to medium low and cover. Simmer for 20 minutes or until quinoa is tender. Stir in thawed corn (if using). Season with salt and pepper.
3. To make the sauce, mix the tomato sauce and the reserved tomato juice in a bowl. Season with cumin and chipotle chili powder. Stir until combined. Prepare drizzle by combining vegan mayo, ketchup and lime juice in another small bowl.
4. To prepare burritos, spread a little bit of sauce in the bottom of a baking dish. Fill a tortilla generously with the quinoa mixture. There will be a lot of filling so don't be afraid to fill them to bursting. Roll the tortilla closed and place seam side down in the baking dish. Proceed with the rest of the tortillas.
5. Pour remaining sauce on top of all the burritos. Drizzle with vegan mayo/lime juice mixture. Bake uncovered for 20 minutes.
Source of recipe: Adapted from a recipe I found in Vegetarian Times.