Preheat oven to 180 degrees C. Grease and flour two 20cm round cake tins.
In a large bowl, cream butter and 1/2 cup sugar until light and fluffy. Add egg yolks and 1/2 teaspoon vanilla. Beat well. Stir together flour, baking powder and salt. Add to butter mixture alternately with milk. Pour into cake tins.
Wash and dry beaters and bowl thoroughly. In a large bowl beat egg whites, 1 teaspoon vanilla and the rum essence until soft peaks form. Gradually add the remaining 1/2 cup sugar. Continue beating until stiff peaks form. Drop small spoonfuls of meringue over unbaked batter in tins, then carefully spread out to cover. Sprinkle pecans over meringue and press lightly into surface.
Bake at 180 degrees C for 25 to 30 minutes or until a wooden toothpick inserted in centre comes out clean. Cool cakes in tins for 10 minutes.
Carefully remove from tins. Turn cake layers meringue side up and let cool thoroughly. About 1 to 2 hours before serving, make the filling: Combine whipping cream, icing sugar and the remaining 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 1 to 2 hours. Store in refrigerator.