PREHEAT oven to 350°F. Melt 1/4 cup of the butter in small saucepan on medium heat. Add 1/4 cup of the sugar; cook 1 min. or until sugar is completely dissolved, stirring occasionally. Pour into 9-inch round cake pan. Top with the plums; sprinkle with almonds. Set aside.
BEAT remaining 1/2 cup butter and remaining 3/4 cup sugar in medium bowl with electric mixer until light and fluffy. Add eggs, one at a time, beating well after each addition. Blend in extract. Add flour and baking powder; beat just until blended. Gently spread over plums.
BAKE 40 to 45 min. or until toothpick inserted in center comes out clean. Immediately run knife or metal spatula around rim of pan to loosen cake; invert onto serving plate. Cool completely before cutting into 12 slices to serve.