Sift together flour, salt, baking powder and soda into a large mixing bowl.
In a medium bowl, mix honey together with butter or margarine until creamy. Add to flour mixture along with the oats, egg, grapefruit juice and walnuts. Stir together until smooth and pour into a lightly greased 9x5 inch loaf pan.
Bake at 350 degrees F (175 degrees C) for 1 hour or until a toothpick inserted into the center comes out clean.