Heat oven to 425 degrees. Combine flour and salt in a bowl. Cut in butter with a pastry blender until pieces are the size of small peas. Sprinkle the water gradually over flour mixture, stirring with a fork and drawing flour into a ball. Add just enough water to hold the mixture together and pull away from the sides of the bowl. Pat into a ball and turn out onto a lightly floured board. Roll into a circle and cut shapes to fit small tart pans or muffin tins. Prick each shell with a fork and bake for 12 minutes. Cool. Melt butter in a saucepan. Add lemon juice, rind and sugar. Cook, stirring, until sugar is dissolved. Add eggs and cook, stirring constantly, until thick, about 20 minutes. Cool. Fill tart shells and refrigerate until serving time.