Preheat oven to 350°.
Coat bottom of a 9-inch round cake pan with melted margarine. Sprinkle brown sugar over margarine. Arrange apple slices spokelike over brown sugar, working from center of pan to edge; set aside.
Combine flour and next 6 ingredients (flour through cloves) in a bowl; stir well. Set aside. Beat 1/4 cup margarine and granulated sugar at medium speed of a mixer until well-blended. Add molasses and egg; beat well. Add flour mixture to creamed mixture alternately with yogurt, beginning and ending with flour mixture; beat well after each addition. Stir in dates and walnuts. Pour batter over apple slices.
Bake at 350° for 40 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan 5 minutes on a wire rack. Loosen cake from sides of pan, using a narrow metal spatula. Invert onto a cake plate; cut into wedges. Serve warm.