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1
Make the crust: Preheat oven to 350F.
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2
In a food processor, pulse graham crackers, almonds, and sugar until finely ground; add butter, and process until combined.
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3
Press mixture firmly into the bottom and up sides of a 9-inch tart pan with a removable bottom.
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4
Refrigerate until firm, about 15 minutes.
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5
Make the filling: Carefully wipe processor blade and bowl clean.
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6
Process cream cheese, sour cream, sugar, egg, vanilla, and salt just until smooth.
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7
Place tart pan on a rimmed baking sheet; fill with cream cheese mixture.
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8
Bake until filling is just set, 30 to 35 minutes.
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9
Transfer pan to a wire rack to cool completely.
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10
Make the topping: In a medium saucepan, combine plums, sugar, and lemon juice.
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11
Cook at a low simmer, stirring until mixture has thickened to a jamlike consistency, 15 to 25 minutes (time will depend on ripeness of fruit).
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12
Reserve 1 tablespoon cooking liquid (no solids); cool remaining plum mixture completely.
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13
Leaving a 1-inch border, spread cooled plum mixture over tart filling.
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14
Reheat reserved plum liquid (on stove or in microwave) until loose.
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15
In a medium bowl, combine with blueberries, and scatter on top of plum mixture.
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16
Refrigerate until ready to serve, 2 hours or up to 1 day; unmold before serving.
