Place pie crust in 9-inch tart pan with removable bottom or 9-inch glass pie pan as directed on box for One-Crust Filled Pie. Trim edge if necessary.
Place cookie sheet on middle oven rack in oven to preheat; heat oven to 375°F. In small bowl, mix 1/2 cup flour, the brown sugar and oats. With fork or pastry blender, cut in butter until mixture is crumbly; set aside.
In large bowl, mix granulated sugar and 3 tablespoons flour. Stir in whipping cream, apricot preserves and egg yolk until well blended. Stir in rhubarb. Pour filling into crust-lined pan. Sprinkle topping evenly over filling.
Place tart on preheated cookie sheet in oven; bake 40 to 50 minutes or until filling bubbles around edge and topping is deep golden brown. Let stand 30 minutes before serving.