1. Preheat oven to 400°. Toss together first 4 ingredients and 1/4 cup flour in a large bowl. Transfer to a lightly greased 13- x 9-inch baking dish.
2. Pulse remaining 1 cup flour, brown sugar, and butter in a food processor until crumbly. Stir in hazelnuts, almonds, and salt. Sprinkle nut mixture evenly over apple mixture.
3. Bake at 400° for 45 minutes or until golden brown. Serve hot or at room temperature with crème fraîche.
*To peel hazelnuts, roast at 350° for 6 to 8 minutes, and rub in a towel while warm to remove thin skins.