Heat oven to 375°. Coat a large rimmed baking sheet with cooking spray. In a bowl, toss plums with 1/3 cup sugar and cardamom. Dust flour on work surface; roll out dough to a 14-inch diameter and transfer to baking sheet. Leaving a 2-inch border, sprinkle marzipan on dough. Arrange plums in circular pattern over marzipan. Fold and pleat edges toward center. Brush dough with egg and sprinkle with remaining 1 teaspoon sugar. Bake until crust is golden, 22 to 26 minutes. Cool; serve.
