In a medium bowl stir together flour and salt. Add butter. Using a pastry blender, cut cold butter into flour until mixture resembles coarse meal, leaving some pieced of butter the size of small peas.
In a small bowl stir together the sour cream and 1 tablespoon of the water. Add to the flour mixture and stir with a fork until the mixture starts to clump together. Add the remaining water, if necessary, to moisten. Form into a ball. Shape the dough into a rectangle. Place between 2 pieces of waxed paper or plastic wrap. Roll to 18x9-inch rectangle.
Peel off the top sheet of waxed paper or plastic wrap. Turn the dough over onto a lightly floured surface and peel off remaining paper or wrap. Fold the dough crosswise into thirds, forming a 6x9-inch rectangle. Fold dough in thirds again, forming a thick piece about 3x6 inches. Wrap dough and chill in the refrigerator 1 hour or until firm. (Dough may be chilled up to 24 hours; let stand at room temperature until easily rolled.) For longer storage, wrap in heavy foil. Seal, label, and freeze up to 3 months. Thaw the dough, covered, in the refrigerator overnight before using. Use the dough as directed in Apricot-Almond Breakfast Pastries (see Recipe Center).