Spray a large (at least 10 cups) fluted tube pan with non-stick spray.
Preheat oven to 350F/180C.
Mix flour, baking powder, salt, nutmeg, mace and baking soda in a medium bowl. Set aside.
Using a heavy-duty stand mixer (batter is thick and may be too much for a hand-held) cream the butter and sugar on medium speed until it’s pale and fluffy.
Add eggs, one at a time, beating until combined. Add the vanilla, just until it’s incorporated.
With mixer on low speed, gradually add the flour mixture to the butter mixture alternately with the buttermilk, beginning and ending with the flour. Mix until just combined.
Spoon batter into prepared pan. Tap the pan a few times on the counter to release any air bubbles.
Bake for about 50 minutes or until a toothpick inserted in the center comes out clean.
Cool on a rack for 15 minutes then remove the cake from the pan and invert it so the rough, cracked side is facing upward. Cool completely.
Mix the confectioner’s sugar and water until smooth. Spoon over top of the cake.