Summer plums are stunning and delicious in this plum and almond frangipane tart. This tart is so flavorful served on its own, or make it extra extravagant by serving with sweetened whipped cream or a big spoonful of vanila ice cream. Frangipane is a mixture of ground almonds, sugar eggs, butter, and vanilla and almond extracts. The frangipane filling can be made in advance, refrigerated in an airtight container for up to 3 days. Before using, remove from the refrigerator and let sit at room temperature about 30 minutes to soften, stirring 3 to 4 times.