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["Position rack in center of oven", "", "Preheat to 425 degrees", "", "Toss cauliflower with 1T olive oil in large bowl. Spread on large rimmed baking sheet, spacing apart. Sprinkle with salt and pepper. Roast 15 minutes. Turn florets over continue roasting until tender about 25 minute longer. Cool cauliflower, then thinly slice. Sprinkle with truffle salt, toss.", "", "Reduce oven temperature to 350 degrees", "", "Press piecrust onto bottom and up sides of 9"" diameter tart pan with removable bottom. Line piecrust with foil, fill with pie weights. Bake crust 20 minutes. Remove foil and pie weights, bake until crust is golden, about 5 minutes, pressing crust with back of fork if bubbles form. Cool crust. Maintain oven temperature.", "", "Heat remaining 1 AA1/2 T olive oil in a heavy large skillet over medium heat. Add onion, sprinkle with salt and pepper. Cook until onion is deep golden brown, stirring occasionally about 40 minutes. Cool slightly.", "", "DAY OF SERVING", "", "Brush bottom and sides of crust with mustard.", "Spread onion in crust.", "Arrange cauliflower evenly over.", "Set Tart on rimmed baking sheet.", "", "Whisk eggs and next 4 ingredients in medium bowl. Stir in Gruyere. Pour mixture over filling in tart pan. Sprinkle with Parmesan.", "Bake until tart is golden and center is set, about 40 minutes.", "Transfer to rack,", "Cool 15 minutes before serving."]
