Heat 2 tablespoons olive oil in a large nonstick skillet over medium heat.
Add the diced onion and sauté for about 2 minutes until it begins to soften.
Stir in the diced zucchini, grated carrot, and diced green pepper and sauté another 5–7 minutes until vegetables are tender.
Add the minced garlic and cook about 1 minute until fragrant, stirring constantly.
Mix the tomato paste into the vegetables until well combined.
Pour in the diced tomatoes (14.5 oz can) and 2 cups V8 juice, then stir in dried basil, dried oregano, bay leaf, and sugar.
Bring the sauce to a boil, then reduce heat to a simmer. Cover and simmer at low heat for 30 minutes, stirring occasionally. Add a little water if you prefer a thinner sauce.
Remove the bay leaf, season with salt and pepper to taste, and serve with hot spaghetti and Parmesan if desired.