Preheat oven at 325. Place a baking sheet onto middle rack and remove top rack from oven. Before starting batter, wash jars, lids, and rings in hot soapy wate r and let drain, dry, and cool to room temperature. Generously prepare inside o f jars with margarine. To prepare batter, combine flour, salt, baking soda, ba king powder, cinnamon, nutmeg, and cloves. In another mixing bowl, combine egg whites, sugar, margarine, and zucchini. Divide batter among 4 jars (should be s lightly less than half full). Carefully wipe rims clean, then place jars on bak ing sheet (or they'll tip over) in the center of oven. Bake 40 minutes. Keep l ids in hot water until they're used. When cakes are done, remove jars which are HOT from oven one at a time. If rims need cleaning, use moistened paper towel. Carefully put lids and rings in place, then screw tops on tightly shut. Place jars on a wire rack; they will seal as they cool.
Once jars are cool, decorate with round pieces of cloth. Unscrew the ring (the lid should be sealed by now) and place a few cotton balls on top of the lid (mak es it poofy on top), then a piece of cloth (about 3" larger than the lid) on top and screw the ring back on. Decorate as desired (example pinking shears).