Preheat oven to 375º.
Sift flour, baking powder, salt, and baking soda.
Cream butter, orange rind, and sugar. Blend in the 4 egg whites one at a time, beating well.
Combine orange juice and water.
With electric mixer, alternately add dry mixture and orange juice to the butter mixture. (Begin and end with dry)
Pour into 2- 8 inch round pans, well greased and floured.
Bake for 25-30 minutes. Cool. Split layers to make 4 layers. Spread filling (see below) between layers and on top. Sprinkle with coconut. Frost sides with cool whip.
To make filling:
Combine first 6 ingredients in small pan and cook until bubbly. Remove from heat and add butter and orange rind. Cool.