In a large mixer bowl beat together butter and 1/2 cup granulated sugar until well-combined; add egg yolks and the 1/2 teaspoon vanilla. Beat with electric mixer until light and fluffy. Stir together flour, baking powder, and salt. Add to creamed mixture alternately with milk. Pour into 2 greased and floured 8x1 1/2-inch round cake pans.
Wash and dry beaters. In a medium mixer bowl beat egg whites, 1 teaspoon vanilla, and the rum extract till soft peaks form (tips curl) gradually add 1/2 cup granulated sugar. Beat until stiff peaks form (tips stand straight). Drop spoonfuls of egg white mixture over unbaked batter in pans, then carefully spread out to cover. Sprinkle pecans over egg whites. Press lightly into surface.
Bake in a 350 degree F oven for 25 to 30 minutes or until a wooden toothpick inserted in center comes out clean. Cool in pans 10 minutes. Carefully remove from pans. Turn cake layers meringue side up; cool thoroughly.
About 1 to 2 hours before serving make filling. Combine whipping cream, powdered sugar, and 1 teaspoon vanilla. Beat until soft peaks form. Fold in pineapple. Place one layer, meringue side up, on cake plate. Spread filling over. Place second layer on top with meringue side up. Chill in the refrigerator for at least 1 hour or up to 2 hours. Store leftovers in refrigerator. Makes 10 servings.