Slice bell peppers in half and take out the membranes and seeds. In a large pot, bring water to a boil and add bell peppers. Cook until just tender. Set aside.
Heat oil in a pan and add onions. Cook until translucent.
Crumble tofu and add it to the pan. Cook until starting to brown. Add garlic and cook for 30 seconds more.
Add tomato sauce, chopped green pepper, and spices. Cook until the bell pepper is crisp tender.
Add Roma tomatoes and spinach. Cook until spinach is wilted.
Preheat oven to 350°F.
Stuff pepper halves with tofu mixture. Top with vegan mozzarella. Bake at 350°F for 20-30 minutes, or until bell peppers are tender.