Step 1: Prepare all your vegetables. Cut eggplant, zucchini, bell peppers, and tomatoes into roughly 1-inch cubes. Finely chop the onion and garlic.
Step 2: Heat 2 tablespoons of olive oil in a large, heavy-bottomed pot or Dutch oven over medium-high heat. Add the eggplant and sauté for about 5-7 minutes until lightly browned and softened. Remove with a slotted spoon and set aside.
Step 3: Add another tablespoon of olive oil to the pot, then add the zucchini. Sauté for 4-6 minutes until tender-crisp and lightly browned. Remove and set aside with the eggplant.
Step 4: Add the remaining tablespoon of olive oil to the pot. Reduce heat to medium. Add the chopped onion and cook until softened and translucent, about 5-7 minutes.
Step 5: Stir in the minced garlic and bell peppers. Cook for another 5-8 minutes, stirring occasionally, until the peppers begin to soften.
Step 6: Add the diced tomatoes (fresh or canned), tomato paste, fresh thyme sprigs, rosemary sprigs, bay leaf, salt, and black pepper to the pot. Bring to a simmer, then reduce heat to low, cover, and cook for 20 minutes, allowing the flavors to meld. This is where the magic of a good ratatouille recipe begins to unfold.
Step 7: Return the cooked eggplant and zucchini to the pot. Gently stir to combine all vegetables. Continue to simmer, uncovered, for another 20-30 minutes, or until the vegetables are very tender and the sauce has thickened slightly. For an even richer flavor in your ratatouille recipe, let it simmer longer on low heat.
Step 8: Remove the herb sprigs and bay leaf. Stir in the fresh basil leaves. Taste and adjust seasoning as needed. Serve warm, garnished with extra fresh basil. This ratatouille recipe is best served after the flavors have had a chance to fully develop.