Preheat the oven to 350° F, and butter, or spray with nonstick spray, the pan(s) of your choice: a large (10") tube or bundt-style pan; two 8 1/2" x 4 1/2" loaf pans; or six small loaf pans (about 3 1/2" x 7").
Cake batter
Beat the butter, sugar, nutmeg, and salt until light and fluffy.
Add the eggs one at a time, beating well after each addition.
In a seperate bowl, whisk the flour and baking powder together. Add the dry ingredients to the batter alternately with the eggnog, 1/3 at a time, beating well after each addition. Pour or spoon the batter into the pan(s).
Bake 60 to 65 minutes for the large loaves or tube pan, or 30 to 35 minutes for the small loaf pans, or until a cake tester or toothpick inserted into the center of the cake comes out clean.
Let the cake cool in the pan for 15 minutes, turn it out onto a rack set atop parchment, to catch any of the topping drips.
Topping
Melt the butter, and stir in the brown sugar, corn syrup, and salt, stirring until the sugar dissolves. Bring the mixture to a boil, and continue to boil for several minutes, until it reaches 240° F (soft ball stage) on a candy or instant-read thermometer. Add the flavor and nuts, and pour the toffee topping over the cake. Cool completely before serving.
Notes
Makes 6 small loaves at about 6 slices each loaf. Or makes 2 loaf pan cakes. Or makes one large bundt cake.