Coat bottom of a 9-inch round cake pan with melted margarine. Sprinkle brown sugar over margarine. Place 1 cherry in center of pan; arrange remaining cherries around edge of pan. Combine nectarines and lemon juice; toss well. Arrange nectarine slices spokelike, working from center cherry to edge of cherries.
Lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, almonds, baking powder, baking soda, and salt in a bowl. Beat 2/3 cup granulated sugar and 1/4 cup margarine at medium speed of a mixer until well-blended. Add extracts and egg; beat well. Add flour mixture to creamed mixture alternately with buttermilk, beginning and ending with flour mixture; beat well after each addition. Slowly pour batter over fruit.
Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean. 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.