PreparationMake crust: Mix flour, sugar and salt in processor. Add butter and cut in using on/off turns until mixture resembles coarse meal. Add water by tablespoonfuls and process just until moist clumps form. Gather dough into ball; flatten into disk. Wrap in plastic. (Can be made 1 day ahead. Keep chilled. Let soften slightly at room temperature before rolling.) Preheat oven to 375°F. Roll out dough on large sheet of floured parchment paper to 1/4-inch-thick round. Trim dough to 14-inch diameter. Transfer dough on parchment paper to large baking sheet (edges of dough may hang over edges of baking sheet). Make filling: Mix plums, jam, vanilla, and allspice in large bowl. Mound plum mixture in center of dough, leaving 3-inch border. Sprinkle fruit with 2 tablespoons sugar. Fold dough border over fruit, pleating loosely and pinching to seal any cracks. Bush dough with beaten egg. Sprinkle dough with 1 tablespoon sugar. Bake tart until crust is brown and filling bubbles, about 45 minutes. Transfer baking sheet to rack and cool tart slightly, about 20 minutes. Slide metal spatula under all sides of crust to free from parchment. Using large tart pan bottom as aid, transfer tart to platter. Serve warm or at room temperature with frozen yogurt.
PreparationMake crust: Mix flour, sugar and salt in processor. Add butter and cut in using on/off turns until mixture resembles coarse meal. Add water by tablespoonfuls and process just until moist clumps form. Gather dough into ball; flatten into disk. Wrap in plastic. (Can be made 1 day ahead. Keep chilled. Let soften slightly at room temperature before rolling.) Preheat oven to 375°F. Roll out dough on large sheet of floured parchment paper to 1/4-inch-thick round. Trim dough to 14-inch diameter. Transfer dough on parchment paper to large baking sheet (edges of dough may hang over edges of baking sheet). Make filling: Mix plums, jam, vanilla, and allspice in large bowl. Mound plum mixture in center of dough, leaving 3-inch border. Sprinkle fruit with 2 tablespoons sugar. Fold dough border over fruit, pleating loosely and pinching to seal any cracks. Bush dough with beaten egg. Sprinkle dough with 1 tablespoon sugar. Bake tart until crust is brown and filling bubbles, about 45 minutes. Transfer baking sheet to rack and cool tart slightly, about 20 minutes. Slide metal spatula under all sides of crust to free from parchment. Using large tart pan bottom as aid, transfer tart to platter. Serve warm or at room temperature with frozen yogurt.