Preheat oven to 350 degrees F.
In a saute pan, over medium heat, add 2 tablespoons olive oil. Cook the onions and garlic until soft and glossy, just beginning to brown. Add the tomatoes, cayenne and saffron, and cook for 5 minutes. Add the clams, mussels and white wine. Cover and continue to cook for another 3 minutes. Uncover and remove from heat. Taste and adjust seasoning with salt and pepper. Reserve.
In another saute pan, over high heat, add 3 tablespoons olive oil. Saute eggplant slices until lightly browned. Add green and yellow zucchini. Cook another 1 minute, just until heated. Add 1 tablespoon of chiffonade of basil. Season, to taste, with salt and pepper. Reserve.
Season sea bass fillets with salt and pepper. In another saute pan, heat the remaining 3 tablespoons of olive oil. Sear fillets, meat next to the bone side down first, until golden, about 2 minutes. Transfer pan to oven and continue to cook another 4 minutes. Transfer to burner, turn fillets. Add butter and baste.
To serve: spoon 1/4 of the tomato sauce on plate. Place 1/4 of the Sauteed vegetable slices in the center and top with a piece of sea bass. Garnish with diced bell pepper and remaining chiffonade of basil. Drizzle Basil Oil around edge of tomato sauce.
In boiling salted water, blanch basil leaves for 2 seconds. Refresh in bowl of iced water and drain well. Place on baking tray lined with paper towel and let dry for 1 hour. Pour oil in a blender. Turn machine on to puree and slowly add the blanched basil. Continue to process until pureed and well blended. Transfer to a squirt bottle and allow to steep for a few hours. Use as needed.