Mix together flour, butter, and ¼ cup brown sugar. Press firmly into the bottom of a lightly greased 13x9-inch pan. Bake for 10 minutes at 350 degrees F. Cool. Mix together the eggs, 2 cups brown sugar, and salt. Stir in coconut, raisins, walnuts, lemon juice and rind. Spread evenly over the partially baked bottom layer. Bake for about 20 minutes at 350 degrees F. Top will be lightly browned. When cool, cut into bars. If desired, sprinkle with confectioners sugar before serving.