3 tablespoons apricot jam, melted, strained, and kept warm
vanilla ice cream as an accompaniment if desired
Preheat oven to 400°F. Scrape seeds from vanilla bean with a knife into a small bowl, discarding pod, and stir in sugar and cinnamon.
On a lightly floured surface roll out pastry 1/8 inch thick and drape pastry over tart pan, pressing dough gently onto pan.
On pastry arrange plum and apricot slices, overlapping them slightly, in rows and sprinkle with sugar mixture.
Bake tart in middle of oven until pastry is golden brown, 20 to 25 minutes.
Cool tarts on a rack and brush with jam. Serve tarts warm with ice cream.