Heat 2 tablespoons olive oil in a large nonstick skillet over medium heat.
Add the diced onion and sauté for about 2 minutes until beginning to soften.
Add diced zucchini, grated carrot, and diced green pepper and continue to sauté for 5–7 minutes until vegetables are tender.
Stir in the minced garlic and cook about 1 minute until fragrant.
Mix the tomato paste into the vegetables until evenly coated.
Add the diced tomatoes (14.5 oz can), tomato paste (if not already added separately), 2 cups V8 juice, dried basil, dried oregano, bay leaf, and 1 1/2 tablespoons sugar; stir to combine.
Bring the sauce to a boil, then reduce the heat to a simmer.
Cover and simmer for about 30 minutes, stirring occasionally; add a little water if you prefer a thinner sauce.
Season with salt and pepper to taste, remove and discard the bay leaf, and serve over hot spaghetti with parmesan if desired.
