- Heat oven to 350°F and put a rack in the center. Grease two 9" round cake pans (or whichever cake pans you'd like to use), line with parchment, and grease again.
- In a mixing bowl whisk together the flour, baking powder, salt, nutmeg, and cinnamon until well combined. Meanwhile, in the bowl of a standing mixer fitted with the paddle attachment, beat the sugar and the butter until very light and fluffy, at least 8 minutes. Scrape down the bowl half-way through.
- Add the eggs one by one to the butter mixture with the mixer on low, fully incorporating one before adding the next. add the vanilla. add about a third of the flour, then a third of the coke, repeat until they're both all added. after the last addition, turn the mixer off and finish mixing gently by hand with a rubber spatula, making sure to scrape the bottom of the bowl.
- Divide the batter between 2 9" cake pans, about 26 oz of batter per pan. Bake on the center rack for 25-30 minutes or until a cake tester inserted in the center comes out clean. Allow cakes to cool for about ten minutes in the pan and then invert onto cooling racks.
- To make the frosting rub down the bowl of a stand mixer with a wedge of lemon, and then whip the egg whites and a pinch of cream of tartar with the whisk attachment until stiff peaks form. Turn the mixer off. While the egg whites are whipping, heat the coke, sugar, and vanilla in a medium sauce pan over medium heat, stirring to dissolve the sugar. Once dissolved, turn the heat to high and boil until it reaches the soft ball stage or 240°F on a candy thermometer.
- With the mixer on low slowly pour the hot syrup into the stiff egg whites, increasing the speed to medium high once all the syrup has been added. Beat until the bowl is cool to the touch, and then proceed to beat in the butter bit by bit until it's all incorporated. If it appears to curdle, don't worry, continue to beat until it's smooth. Be careful not to add the butter while the mixture is still warm or you'll end up with a soupy mess on your hands!
- Frost your cake as desired. The cakes can be frozen and the frosting can be made ahead of time, but bring to room temperature before using.