Italian Rum Cake

PREHEAT OVEN TO 350F. Beat the yolks and 1/4 cup sugar together in a mixing
bowl and slowly add 1/4 cup flour. Meanwhile, place the milk in a small pot
and bring to the brink of boiling. Slowly pour the milk over the yolk
mixture, then pour the whole thing back into the pot. Place over medium
heat and cook, stirring constantly, until the mixture thickens. Remove from
the heat and mix in the lemon peel. Scrape into a plastic container, cover
and place in the refrigerator to chill. Running your mixer at high speed,
cream butter and remaining sugar together in a mixer fitted with a paddle.
Add the eggs 1 at a time, waiting until the previous 1 has been absorbed.
Add the sour cream and mix until incorporated. Add vanilla, nutmeg, baking
soda and salt. Decrease the speed to medium, add remaining flour and mix an
additional minute. Scrape the batter into a 1-quart round or rectangular
cake pan, leaving 1/2-inch space at the top. Place on the middle rack of
the oven for 50-to-60 minutes. The cake is done when the surface cracks and
a toothpick inserted into the center comes out clean. Remove cake from the
oven and let cool for 15 minutes before unmolding onto rack. When the cake
is completely cool, slice it into 6 layers. Place the first layer on a cake
platter and sprinkle with some of the rum. Cover the layer with some of the
custard mixture. Place the second layer on top of the custard, sprinkle
with rum and cover with more custard. Continue until the cake is assembled.
Lightly spread the custard all over the surface of the cake. Refrigerate
for 2 hours before serving.