Without washing beaters, in a small bowl beat yolks until thick and lemon-colored. In a large bowl, cream shortening and sugar until fluffy and well-blended. By hand or with slowest mixer speed, add dry ingredients to this mixture, alternating with orange juice. Do not overmix or layers will fall flat. Carefully fold in stiffly beaten egg whites just until blended.
Folding is meant to preserve as much as possible the air beaten into the egg whites, so be gentle.
Divide batter evenly between pans and bake 30 to 35 minutes, or until a toothpick inserted in the center of each layer comes out clean. Remove from oven and cool layers 10 minutes on a wire rack. Turn out from pans, lift off wax paper and allow to cool on racks, right side up. Continue to set the microwave for 1-minute intervals until mixture boils. Cook 1 minute more while boiling, and you're done.