2 Tbsp olive oil
1 onion, diced
1 eggplant (approx. 12 oz), peeled and cut into 2x1/4-inch strips
1 zucchini, cut into 2x1/4-inch strips
1 cup chopped green beans (cut into 2-inch lengths)
1/2 green (or red) bell pepper, seeds and ribs removed, cut into 2x1/4-inch strips
2 cloves garlic, minced
2 Tbsp red wine vinegar
1 15-oz can tomato sauce
1 Tbsp minced fresh oregano
1 tsp sugar, or to taste
1/2 tsp fresh black pepper, or more to taste
1 small Parmigiano-Reggiano cheese rind (omit for vegan soup)
1 cup vegetable stock
2 tomatoes, diced
1 Tbsp minced fresh basil
Kosher salt, to taste
Shredded Cheddar, Monterey Jack or Parmigiano-Reggiano cheese, for garnish (optional)
In a Dutch oven, heat the oil over medium heat. Add the onion and cook, stirring occasionally, until translucent. Stir in the eggplant, zucchini, green beans, bell pepper and garlic. Sprinkle the vinegar over the vegetables. Cover and cook, stirring occasionally, for 10 minutes to "sweat" and soften the vegetables.
Stir in the tomato sauce, oregano, sugar, pepper and cheese rind (if using). Increase heat to high and bring the mixture to a boil. Reduce to simmer; cover and cook, stirring occasionally, for 30 minutes until the vegetables are tender.
Add the stock, chopped tomatoes and fresh basil, and season to taste with kosher salt (if you've used a cheese rind, you'll need less salt, so taste before you season).
Serve hot, topped with shredded cheese and/or more fresh basil.