Mix together the flours, salt, and sugar. (Do not add the soda yet!) Cut the butter into the flours using a pastry blender or two knives. Grate the zest from about 1/2 of the tangerine and mix this into the flour. Juice the tangerine. Beat the egg with the juice and stir into the flour mix. Fold in the chopped cranberries. The batter should be thin enough that it will not hold peaks. If it is too thick, mix in some milk or water. Have the muffin pans or 3 inch loaf pans greased and ready. Sprinkle the soda over the batter and stir it in quickly. The batter will begin to foam up immediately. Spoon the batter into the muffin pans to about 3/4 of the way to the top. Bake 20 minutes at 350°. This recipe makes nine muffins.