Heat a Dutch oven over high heat then pour in the olive oil. Add in the eggplant and zucchini and season with salt and pepper. Cook, stirring occasionally, until the vegetables start to brown, about 5 minutes.
Mix in the onions, bell pepper, and garlic. Cook for 2 minutes then add in the tomatoes, tomato paste, bay leaf, thyme, herbs de provence, and capers. Season with salt and pepper to taste.
Bring the sauce to a boil, then lower the heat so that it is simmering. Cover and simmer for 30 minutes.
Remove the Dutch oven from the heat and adjust the seasoning if necessary. Enjoy!