Heat oil in a large skillet over medium hear; add the onion, garlic, and pepper. Cook, stirring occasionally until they are softened, 3 to 8 minutes. Stir in tomatoes, herbes de Provence and salt, cover and cook until all veggies are tender about 10 minutes. Taste and adjust seasoning. Stir in basil. Ratatouille may be made one day in advance and kept covered in the refrigerator. Serve chilled at room temperature or reheated. Serves 4.