In a large heavy-bottomed pot or Dutch oven, heat olive oil over medium heat until shimmering. Add diced onion, carrot, and celery. Cook, stirring occasionally, until the onion is translucent and the vegetables begin to soften, about 6–8 minutes.

Add garlic

Add minced garlic and cook 30–45 seconds more, until fragrant but not browned.

Deglaze and add liquids

Pour in the vegetable broth and water, scraping the bottom of the pot to loosen any browned bits. Add the bay leaf and bring the mixture to a gentle simmer over medium-high heat.

Vegetables

Simmer the firm vegetables

Add the diced potato and green beans to the simmering broth. Partially cover and simmer for 8–10 minutes, until the potato is nearly tender.

Add remaining vegetables

Stir in diced carrot (if extra), zucchini, corn, and canned diced tomatoes with their juices. Continue to simmer for another 6–8 minutes until all vegetables are tender but not mushy.

Wilt the greens

Add the chopped spinach or kale in the last 2–3 minutes of cooking and stir until wilted and incorporated.

Legumes / Optional Add-ins

Add beans and grains or pasta

If using canned beans, drain and rinse, then stir them in now to heat through (2–3 minutes). If adding dry pasta, add it to the simmering soup with enough time for the pasta to become al dente (typically 8–10 minutes for small shapes). If using pre-cooked rice, stir it in just to warm (1–2 minutes).

Seasoning & Finish

Season

Stir in dried thyme, dried oregano, salt, black pepper, and red pepper flakes (if using). Taste and adjust salt and pepper as needed. Remove and discard the bay leaf.

Brighten and finish

Turn off the heat and stir in fresh lemon juice and chopped parsley. If desired, ladle soup into bowls and top with grated Parmesan cheese.

Serve

Serve hot in a cup for a light portion or a bowl for a full portion. Leftovers keep covered in the refrigerator for 3–4 days; reheat gently on the stove.