Grease and flour a 10 inch tube pan. Sift together the flour, and baking powder. Set aside.
In a large bowl, cream together the shortening, 1 cup butter and sugar until light and fluffy. Add the eggs one at a time, beating well with each addition, then stir in the vanilla. Add the flour mixture alternately with milk; beat well. Stir in the 3/4 cup crushed pineapple.
Pour into 10 inch tube pan. Place in cold oven. Turn oven to 325 degrees F (175 degrees C) and bake for 90 minutes or until top springs back when touched. Remove from oven and let stand for 10 minutes. Remove carefully from pan.
To make the glaze: In a small saucepan, combine 1/4 cup butter, confectioners sugar and 1 cup crushed pineapple. heat and stir until melted. Pour over cake as soon as it comes out of the pan.