Inspired by the coconut rum I picked up in Honolulu, this delicious cake combines many flavors of the Hawaiian islands. It’s like a luau in your mouth!
This cake began with an impulse buy. I was momcationing in Honolulu, and popped into one of those ubiquitous ABC Stores. The ABC Stores are absolutely over priced on some items, but absolutely convenient: They have EVERYTHING and they are EVERYWHERE. I was on the hunt for a particular nut butter that I had purchased there on a previous trip: macadamia nut honey coconut peanut butter. It sounds like a mouthful, and that’s fitting because I just want to eat it by the spoonful. It’s so perfect on top of my favorite buckwheat waffles that I almost don’t want to make them without this nut butter.
I scoured every ABC Store in Waikiki and didn’t find it, but the sampler pack of Koloa rums did catch my eye. On tasting them with my husband after returning home, we were particularly taken with their coconut rum. It’s amazing in a cocktail, but this rum begged for something a little more special. Remembering the rum cakes that my aunt made years ago, that us kids were never allowed to taste, I wondered how a coconut version might fare. Perfectly, it turns out!
We begin by making a grilled pineapple curd for the cake’s filling. You can make the rum cake without it, but you’d be missing out. The mellowed pineapple layer of flavor really takes this cake to the next level!
Next up to bat is the batter, and we start with flour. You may use traditional all purpose flour, or any gluten free all purpose flour. I’ve made it several times now using a variety of ready-made gf flour blends. They’ve all turned out really well, but my favorite for texture and flavor is Cup 4 Cup’s Multipurpose Flour. It’s so good that your celiac friends just might corner you to verify that it is truly gluten free!
Whatever gf flour you use, when baking you need to look at one thing in particular: xanthan gum. Xanthan gum is essentially a gluten substitute. Some all purpose gluten free flours already contain it, and some don’t. If your gf flour does not, you’ll need to add it or one of the other gluten stand-ins!
Gluten is the “glue” that holds everything together in baking. When gasses bubble up as our baked goods cook, gluten provides the structure and elasticity to allow dough and batter to stretch and rise and contain those gasses. Without it, our breads and cakes become a flat, crumbly mess. We need to replace that gluten with something else in gluten free baking. Xanthan gum is the most common gluten substitute because it most closely approximates the results we get with gluten, but there are other options: guar gum, psyllium fiber, agar agar, and more. We’ll explore this more in a future post, but for now, the general rule is to add around 1/2 tsp xanthan gum per cup of gf flour for cookies and cakes, and 1 tsp per cup of flour for breads.
The next addition to your mixing bowl is 1 cup of coconut flour. It has a delightful flavor, and definitely adds a pleasant texture and chew to baked goods. Being high in fiber and protein, we can almost pretend for a hot minute that this cake does something good for us, too! For a grain-free alternative, you can absolutely skip the all purpose flour altogether and make this with 2 cups of coconut flour. It comes out a bit more dense, a lot more filling, and extremely satisfying. Usually, you would need to add more liquid ingredients when baking with coconut flour as it is surprisingly absorbent, but that isn’t a problem with this extremely moist cake! Make it as-is or add more of the rum syrup at the end to achieve that glistening, saturated goodness typical of rum cakes, whichever you prefer!
With your flours, sugar, pudding mix, baking powder, and salt in the mixing bowl, it’s time to add your room temperature butter and vegetable oil. I have a confession to make here. I’m a butter snob, and unapologetically so. Given the access and the funds, I will splurge on cultured European butter for baking every time – especially in a cake as rich as this one. Cultured butter has been treated with bacterial cultures, much like yogurt, and this adds flavor. European butter has a higher butterfat content than most American butters, and makes for richer dishes. I challenge anyone who thinks this is silly to bake two batches of your favorite cookies: one with a standard butter, and one with the best stuff you can find (which may be in the artisan cheese section of your grocery store). Gather your friends and family for a taste test, and I promise you’ll all be infected with buttersnobitis, too! Once afflicted, Kerrygold and Lurpak are both outstanding, and easy enough on the wallet for every-day meals. When you want to bang on the big drum, try Échiré, the butter with a cult following.
Mix on medium speed until you have a sandy consistency, then add your room temperature milk, still mixing. Add your room temperature eggs one at a time. Pause the mixer, scrape down the sides of the bowl, and mix again until well combined.
Let’s pause our discussion here too, and talk about why we want room temperature ingredients when baking. Simply put, cold ingredients won’t incorporate as evenly as they would at room temp, leading to clumpy batters with less air whipped into it, and a less fluffy cake. If you’re deep into your recipe and realize that you forgot to take something out of the fridge ahead of time, we have some easy fixes.
Now it’s time to add your coconut rum and vanilla or coconut extract, and you have some choices to make. I’ve made this cake with Malibu Rum and Koloa Coconut Rum. Malibu made it sweeter, and Koloa had a more crisp and fresh coconut flavor. The Koloa was definitely also more potent, with 40% alcohol by volume compared to Malibu’s 21%. Both versions were fantastic! There are many other coconut rums out there on the market, and we’d love to hear what you used and how it turned out! Drop us a line or feel free to leave a comment below!
I prefer using vanilla extract here when I’m going for a smoother, richer overall cake, or coconut extract when I really want to highlight that flavor. The choice is yours, and you can’t go wrong either way!
Take a minute to paint some Perfect Pan Release into every nook and cranny of your favorite bundt pan. This stuff is the bomb! It’s a baker’s secret weapon and virtually guarantees a perfect bundt cake every time.
Now divide your batter, and add the chopped macadamia nuts to one half. Place the nutty half of the batter in the bottom of the bundt pan, and spoon the grilled pineapple curd into the middle of the batter, all the way around the pan. Pour the rest of the batter into the bundt pan, atop the filling, and bake in the oven for 50-60 minutes.
When finished and while cooling, make the rum syrup. Combine the butter, water, sugar, salt, and rum to a small sauce pan, and bring to a boil. Reduce the heat and simmer 5-10 minutes to thicken, adding the vanilla extract at the end. Using a skewer, poke holes down through your cake, all the way around. Pour the rum sauce a bit at a time all over the cake, using it all. Cover and let sit overnight.
Now for the moment of truth: getting this sticky cake out of the pan in one beautiful piece. Start by filling your sink or large basin with an inch or three of very hot water. Sit your bundt pan in the hot water for a couple of minutes to loosen up the sticky rum sauce. Remove from the sink, place an upside-down cake stand or plate over the opening of the bundt pan, and carefully invert. If you’ve used the homemade pan release, it should loosen quickly and easily. I’ve made dozens of bundt cakes using the pan release, and it’s been perfect every time! If it doesn’t let go, let it sit for a bit or give it some light taps all around. For a stubborn cake, carefully turn it over again and repeat the hot water trick or warm for 10 minutes in a 350°F oven and try again.
Your cake is ready to serve! Turn up the tunes, kick back with some strong Kona coffee, and get your Hawaiian vibes flowing! Enjoy!