GRATIN OF FLOUNDER

Steps:

• Place each fillet on a flat surface, one at a time. Cut lengthwise on both sides of the small bone line down the center. Discard the bone line. Sprinkle the fillet halves with salt and pepper. Sprinkle with basil and 1 tablespoon of olive oil. Let stand 1 hour.
• Cut the onions in half crosswise. Place each onion half on a flat surface and cut each crosswise into thin slices. There should be about 9 cups.
• Trim off the ends of the zucchini. Cut each zucchini crosswise into 1/4-inch-thick slices. There should be about 5 cups.
• Cut the tomatoes crosswise into 1/4-inch-thick slices. There should be about 5 cups.
• Heat the 1/4 cup olive oil and the butter in a large heavy skillet and add the onions. Cook, stirring, about 10 minutes and add 6 sprigs of the fresh thyme or 1 teaspoon dried thyme, the garlic, salt and pepper. Cook, stirring and scraping from the bottom, about 5 minutes longer or until the onions take on a deep golden color.
• Select an oval baking dish measuring about 13 by 9 by 2 inches. Spread the onions over the bottom, smoothing over the top. Let cool.
• Meanwhile, preheat the oven to 400 degrees.
• Arrange the fillet halves neatly on top of the onions, edges slightly overlapping.
• Neatly arrange overlapping rows of tomato and zucchini slices over the fish.
• If fresh thyme is used, remove the leaves from the remaining sprigs and sprinkle the top of the vegetables with the leaves. If dried thyme is used, sprinkle what remains over the vegetables. Sprinkle salt and pepper over all. Sprinkle with the remaining 1 tablespoon oil.
• Cover closely and tightly with aluminum foil. Place in the oven and bake 30 minutes. Remove the foil and return to the oven. Bake 30 minutes longer.
• Carefully pour the liquid that accumulates in the dish into a saucepan, trying not to disturb the pattern of the vegetables. Place the saucepan on the stove and cook until the liquid is reduced to about 1/3 cup.
• Meanwhile, preheat the broiler.
• Brush the top of the tomatoes and zucchini with the reduced sauce. Pour over any remaining sauce.
• Place the dish under the broiler and glaze the top about 3 minutes. Sprinkle with parsley and serve.