Cream together butter and sugar; beat in egg yolk. Sift together the flour and cinnamon; add to creamed mixture gradually, stirring to blend. Spread dough evenly in a lightly buttered 15x10x1-inch jelly roll pan. Beat egg white slightly; spread over top, smoothing with fingertips. Sprinkle chopped Macadamia nuts evenly over the dough. Bake at 275° for 1 hour. Cut into strips, squares, or triangles while still warm.
Makes about 3 dozen cookies
Calories per cookie/bar: 121