Cream butter; gradually add sugar, mixing well. Add molasses and eggs; beat well.
Combine flour, cream of tartar, and spices.
Dissolve soda in warm milk; add to creamed mixture alternately with flour mixture, beginning and ending with flour mixture; beat well after each addition. Stir in the remaining ingredients.
Pour batter into a greased and floured 13- x 9- x 2-inch baking pan. Bake at 350° for 35 minutes or until a wooden pick inserted in center comes out clean. Cool completely. Cut into squares to serve.