Preheat oven to 350. (325 if using a glass dish). In a small bowl combine sweetened condensed milk, lemon juice and rind; set aside. In large mixer bowl, beat butter and brown sugar until fluffy; add flour, oats, baking powder and salt. Mix until crumbly. Press half of the oat mixture into bottom of a lightly greased 13" x 9" baking pan. Then spread with lemon/milk mixture. Stir spices into remaining crumb mixture; sprinkle evenly over lemon layer. Bake 20-25 minutes or until lightly browned. Cook, then chill. Cut into bars and store.