Prepare veggies : Dice eggplant and sprinkle lightly with salt; let sit 10 minutes, then pat dry (helps reduce bitterness).
Cook onion and peppers : Heat olive oil in a large pot. Add onion and bell pepper; sauté until softened.
Add garlic and root vegetables : Stir in garlic and carrots; cook 1–2 minutes until fragrant.
Add eggplant and zucchini : Cook 5–7 minutes, stirring occasionally, until they soften and brown slightly.
Build the soup base : Add tomatoes, broth, bay leaf, thyme, oregano, salt, and pepper. Stir well.
Simmer : Bring to a boil, reduce heat, simmer 30 minutes until vegetables are tender and flavors deepen.
Finish : Remove bay leaf, taste, and adjust seasonings. Add fresh basil just before serving.