Preheat the oven to 350. Beat together the butter and sugar until light and fluffy. Add the eggs, one by one, then the lemon rind, rum, vanilla, and salt. Don't worry if the mixture looks curdled, adding flour will fix it.

Warm the cocoa, milk, and the 3 tablespoons sugar together to dissolve the sugar and make a dark cocoa syrup. Sift the flour and baking powder together and add in three batches to the egg, sugar, and butter mixture alternating with the 1/2 cup warm milk, beating between each addition. When the batter is smooth, divide it in half and mix the cocoa syrup into one half.

Fill a buttered and floured 9 in. loaf pan with alternate layers of the two batters: white, chocolate, white, chocolate,white. Use a knife to swirl the two batters together. Do it with a light tough and do not blend them.

Bake for 60 to 70 minutes until the cake tests done. Cool on rack for 5 minutes, then unmold. Serve as it, or drizzled with chocolate rum glaze.

CHOCOLATE RUM GLAZE:

3 oz. semisweet chocolate

3 Tbs.rum

3 Tbs. water

1 Tbs. instant coffee

3 Tbs. butter, softened

Melt together the chocolate, rum, water and coffee in a double boiler over low heat. Whisk in the butter until smooth. let this cook for about 10 minutes until slightly thick and drizzle over the cake.