Crust: 
 six 5"x 2-1/2 graham crackers 
 1-1/4 cups coarsely crushed amaretti (Italian almond macaroons, about 3 oz.) 
 3 tablespoons sugar 
 3 tablespoons unsalted butter, melted
 Filling:
 1-1/2 cups mascarpone cheese (about 3/4 lb. at room temp) 
 1/2 cup sugar 
 2 large eggs 
 1 tablespoon fresh lemon juice 
 2 teaspoons freshly grated lemon zest 
 1 teaspoon vanilla extract 
 1/4 teaspoon almond extract 
 3 tablespoons all purpose flour 
 1/4 teaspoon salt 
 For Topping
 2 lbs. nectarines (about 8) 
 2 tablespoons sugar or to taste
 Preheat oven to 3500.  Lightly butter a 9 springform pan.  Make crust. 
 In a food processor finely grind graham crackers and amaretti with sugar. 
 Add butter and blend until combined well.  Press mixture onto bottom and
 about 3/4 up the sice of pan.  Bake crust in middle of oven 10-15 minutes
 or until crisp and golden and cool completely in pan on a rack.  Make
 filling.  In a bowl with an electric mixer beat mascarpone with sugar
 until smooth and add eggs, 1 at a time.  Beat well after each addition. 
 Beat in lemon juice, zest and extracts.  Beat in flour and salt until
 combined well.  Pour filling into crust.  Bake tart in middle of oven
 30-35 minutes until pale golden and set.  Cool completely in pan on rack. 
 Remove side of pan and transfer tart to a plate.  Chill tart, covered at
 least 4 hours and up to 24.  Make topping just before serving.  Slice
 nectarines and in a bowl toss with sugar.  Let nectarines stand, tossing
 occaionally, until sugar is dissolved and juices are released, about 5
 minutes.  Mound topping on tart and serve immediately.