• Preheat oven to 350 degrees.

Bake eggplant and tomatoes

• Place chopped eggplant in a colander and toss with 1 ½ teaspoons salt. Let sit 20 minutes, rinse, and then squeeze out excess liquid. Toss with a tablespoon of olive oil, sprinkle with salt and pepper, and bake in the oven for 25 minutes, or until lightly browned.
• For canned whole tomatoes, break them up into 1-inch pieces with a knife, or with your fingers. Pour into in a baking dish, add half the garlic, and drizzle with two tablespoons olive oil. Bake until thickened, about 30 minutes, stirring every 10 minutes.
• For fresh tomatoes, blanch them first to remove their skins. Bring water to a boil in a medium saucepan. Slit the tomatoes with a knife and submerge in boiling water for 30 seconds. Use a slotted spoon to remove the tomatoes and shock in a bowl of ice water until cool. Remove the skins, and chop into 1-inch pieces, preserving the juices as you do so. Bake as described in the previous step.

Finish the ratatouille

• While the tomatoes and eggplant bake, prepare the rest of the vegetables. Start sautéing after at least 20 minutes of baking time has already passed.
• Add 3 tablespoons oil to a large (large enough to fit the entire recipe) saucepan over medium heat. Add onion and remaining garlic, stirring occasionally until translucent, about 5 minutes. Add peppers and sauté another 5 minutes. Season with salt and pepper.
• Add cooked tomatoes, cooked eggplant, zucchini, bay leaf, and oregano. (If tomatoes and eggplant are still finishing up in the oven, add only the zucchini and herbs until the former are ready.) Stir well and bring to a boil. Reduce heat to medium-low, cover, and cook at a gentle simmer until vegetables are cooked to your liking. If you prefer the vegetables just tender, it will take about 15 minutes. If you prefer the vegetables well-cooked, it will be more like 30 minutes.
• Add vinegar and stir well. Taste, and adjust salt, pepper, and vinegar to taste. Remove bay leaf before serving.