In a medium bowl, cream margarine and sugar, beating until light and fluffy. Stir in egg white and almond extract.
Gradually stir in flour, baking soda, and cream of tartar; mix well. Form into 1/2-inch (1.25 cm) balls. Place on a nonstick cookie sheet at least 2 inches (5 cm) apart. Dip a flat-bottomed glass into flour and press down on each ball to flatten cookie. Top each cookie with an almond slice.
Bake for 8 to 10 minutes, until lightly browned. Cool on pan for 3 minutes, then transfer to wire racks to cool.
