Mascarpone Cheesecake Tart with Nectarines

Crust: 
6        Graham crackers (5 x 2-1/2")
1 1/4 c  Amaretti (Italian almond macaroons, 3 oz); coarsely crushed
3     tb Sugar 
3     tb Unsalted butter; melted
Filling:
1 1/2 c  Mascarpone cheese (3/4 lb); at room temperature
  1/2 c  Sugar 
2     lg Eggs 
1     tb Fresh lemon juice 
2     ts Freshly grated lemon zest 
1     ts Vanilla extract 
  1/4 ts Slmond extract 
3     tb All purpose flour 
  1/4 ts Salt 
Topping:
2     lb Nectarines (about 8) 
2     tb Sugar; or to taste

Preheat oven to 350°F.  Lightly butter a 9" springform pan.

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.

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.

Topping:

Slice nectarines and in a bowl toss with sugar.  Let nectarines
stand, tossing occasionally, until sugar is dissolved and juices are
released, about 5 minutes.  Mound topping on tart and serve
immediately.