1-1/4 cups all-purpose flour
1/2 cup (1 stick) butter, room temperature
2 tablespoons sour cream
About 6 medium apples, peeled, pitted, and sliced
3 large egg yolks
3/4 cup sour cream
3/4 cup sugar
1/4 cup all-purpose flour
1 tsp vanilla
1/2 cup apple jelly
½ tsp ground cinnamon
Whipped cream, if desired
Preheat the oven to 375° F.
Crust: Place the flour, butter, and sour cream in a food processor and pulse to combine. When the dough has formed a ball, pat with lightly floured hands into the bottom and sides of an ungreased 10-inch tart pan with a removable bottom and 1/2-inch sides, or a round au gratin dish. Bake for about 18 minutes, until the crust is set but not browned. Let cool while preparing the filling.
Lower the oven temperature to 350°F.
Filling: Peel and thickly slice the apples. Arrange the apple slices in overlapping circles on top of the crust, until it's completely covered. Overfill the crust, as apples will shrink during cooking. Combine the egg yolks, sour cream, sugar, and flour and beat until smooth. Pour the mixture over the apples. Place the tart pan on a baking sheet and bake for about 1 hour, until the custard sets and is pale golden in color. Cover with an aluminum foil tent if the crust gets too dark. Transfer the tart pan to a wire rack to cool. When cool, remove the side wall of the pan.
Glaze: Combine the jelly and cinnamon. Spread with a pastry brush over the top of the warm tart. Serve the tart warm, at room temperature or chilled.