Preheat oven to 350 degrees F (175 degrees C). Lightly grease one 13 x 9 inch cake pan or two 8 inch round cake pans.
Mix sugar and flour together. With two knives or a pastry blender cut the shortening into the flour and sugar until the mixture resembles coarse crumbs (as if you were making pie dough). Reserve 1/2 cup of this mixture as crumbs for top of cake.
To the remaining flour mixture stir in the baking powder, eggs, milk, and vanilla and mix well. Pour batter into prepared pan. Sprinkle reserved crumb mixture over top.
Bake at 350 degrees F (175 degrees C) for about 45 minutes (35 minutes if using two 8 inch round cake pans) or until center of cake springs back when lightly touched or a toothpick inserted in the center comes out clean.