1. Heat 2 tbsp oil in a large skillet over medium heat. Add eggplant and season with ¼ tsp salt.
2. Cook for about 10 minutes, or until eggplant starts to brown, stirring occasionally.
3. Transfer eggplant to a plate and set aside. Return skillet to the heat and add another 1 tbsp of oil.
4. Add zucchini, onion, and bell pepper to the skillet. Cook for about 10 minutes, stirring occasionally.
5. Add the eggplant back to the pan, along with garlic, diced tomatoes, tomato paste, thyme, sugar, remaining ¼ tsp salt, and red pepper flakes, if desired. Stir to combine.
6. Bring mixture to a boil, then reduce heat to low and simmer for 10 minutes, or until vegetables are tender.
7. Serve warm, topped with fresh basil, if desired.
Adapted from: https://www.onceuponachef.com/recipes/ratatouille.html#tabrecipe
