Beat the butter and sugar with an electric mixer until very light and fluffy, about 2 minutes. Add the zest and mix well. Beat in the egg yolks, one at a time.
Grind the coriander seeds to a fine dust. Combine with the nutmeg, salt, flour and cornmeal. Add to the butter mixture. Beat in the sherry, bourbon and brandy.
Whip the egg whites (salt and cream of tartar help stabilize them) until soft peaks form. Fold one-third of the egg whites into the batter to lighten. Fold in remaining egg whites.
Pour into a greased 9-inch loaf pan. (If your loaf pan is 7 inches, you'll have enough batter left for a large muffin or two). Bake at 325 for 90 minutes. Cool slightly in pan, then turn out and cool completely.