How to Make It
Preheat oven to 350. Place softened butter and sugar in the bowl of your stand mixer with a paddle attachment, or in a large bowl with your hand mixer and beat until light and fluffy, about 3-5 minutes. Add eggs one at a time and beat until well mixed. Add the cola, vanilla and rum and blend.
In a large bowl, whisk the dry ingredients to blend and break up any clumps and add to the bowl and mix until smooth.
Line a large loaf pan with a sheet of parchment paper and spray with cooking spray, or spray a nonstick Bundt pan with cooking spray, and add your batter, smoothing the top.
Bake for 75-90 minutes, or until the top has risen and cracked a bit and a skewer in the middle comes out clean.
While the cake is baking, mix the zest and juice of one large lime with 2 cups of confectioners’ sugar. Cool in the pan on a rack for 5 minutes. Then drizzle or spread 2 tablespoons of the glaze over the top, where it will melt in and help seal the cake, then cool in the pan for another 15 minutes. Gently remove from the pan and cool completely on a rack. When cooled, drizzle as much of the glaze over as you like.
This is a dense cake and no one’s oven is the same. You want a deeply cracked, well-browned top crust, and the skewer must come out clean or the cake will be doughy and taste of raw flour.
Since every lime is different, you might need more sugar if the glaze is too liquid. I like some thickness, about the consistency of pancake batter, so that it will still drizzle, but slowly like lava. I like a full coating on top with some waterfall over the sides, but some prefer a lighter drizzle and some like to spread evenly over the whole cake.