Combine flour, baking powder, and salt; stir well. Cut in shortening with a pastry blender until mixture resembles coarse meal. Gradually stir in water, mixing well.
Shape dough into 1/2-inch balls, and place on a lightly floured surface. Roll each ball into a very thin circle about 4 inches in diameter.
Heat an ungreased cast-iron griddle over medium heat; cook tortillas 2 minutes on each side or until lightly browned. Pat tortillas lightly with spatula while browning the second side if they puff during cooking. Serve hot with butter, if desired.
Note: Tortillas may also be cooked in an ungreased electric skillet heated to 375°.