PREHEAT oven to 350°F. Mix flour and 1/4 cup of the sugar in medium bowl. Cut in butter until mixture resembles coarse crumbs. Stir in almonds. Add water; stir until dough forms a ball. Press onto bottom and up side of 9-inch tart pan. Bake 10 min.
PLACE cream cheese, almond paste, 2 Tbsp. of the sugar, the egg and vanilla in food processor container; cover. Process until smooth. Pour into crust. Drain plums, reserving liquid. Remove and discard pits from plums. Place plums and 1 Tbsp. of the sugar in food processor container; cover. Process until smooth. Spoon over cream cheese mixture. Cut through batter with knife several times for marble effect.
BAKE 25 min. Cool. Refrigerate several hours or until chilled.
MIX cornstarch and remaining 1 Tbsp. sugar in small saucepan. Gradually add reserved plum liquid, mixing well until blended. Bring to boil on medium heat, stirring constantly. Boil 3 min. or until clear and thickened, stirring constantly. Serve with the tart.