Preheat oven to 325ºF. Line a 9-inch loaf pan with a sheet of parchment paper long enough to hang over the sides.
Combine the butter and granulated sugar in a large bowl. Beat until fluffy, and well mixed. Add the molasses, vanilla and the eggs, one at a time, making sure to beat each one until the batter is light and fluffy again before adding the next egg.
Add the flour, baking powder, salt, ginger, cinnamon, and cloves. Beat until just mixed, and there are no visible signs of flour. Add the buttermilk, and beat again until just mixed; 15 to 30 seconds should do it.
Scrape the batter into prepared loaf pan, and bake about 75 minutes, until deep golden on top and a metal skewer inserted in the center comes out clean. Set the cake on a wire rack to cool completely before glazing (or serving if leaving plain).
Once the cake is cooled, prepare the glaze. Whisk together the confectioner’s sugar and 4 teaspoons of eggnog until the sugar is completely dissolved, Whisk in the melted butter. If you want a thinner glaze, whisk in the remaining teaspoon of eggnog. Drizzle over the top of the cake. Sprinkle the candied lemon on top, as much or as little as you like. Let glaze set for at least 20 to 30 minutes before serving.