Preheat oven to 325° and grease a 8½- by 4½- by 2½-inch loaf pan.
Sift together flour, salt, baking powder and set aside. Using an electric mixer, cream butter and sugar until light and fluffy. Add citrus zest and 2 unbeaten eggs, 1 at a time, and beat well. Add vanilla and nutmeg to milk. Then, slowly mix dry ingredients into batter alternately with milk. Do not over mix or the cake will become tough. When just combined, pour into loaf pan and bake until golden brown and a skewer inserted into the middle comes out clean, about 1½ hours. Cool on a rack 10 minutes before removing from pan.
Adapted from Mrs. Phyllis Jameson Grant, Block Island Cookbook: A Collection of Favorite Recipes.