Zest the lemons directly into the sugar, scrinching it with your fingers to get all the lemony flavor into the sugar. Stir your zesty sugar with the lemon juice, egg yolks, and a small pinch of salt in a medium saucepan.
Cook over medium low heat, stirring constantly, until it begins to thicken. Continuing to stir, drop in your butter piece by piece, waiting for each bit to melt before adding the next one. Continue to cook until the mixture coats the back of your spoon and running your finger through leaves a nice clean trail. Lick your finger. It’s worth it! You’ve made lemon curd!
Transfer the curd into a bowl, using a small strainer. Press the curd through the strainer with a rubber spatula to remove the zest (it’s fulfilled its zippy destiny) and any possible egg or shell bits. Press plastic wrap directly on the surface of the curd and refrigerate while we make and cool the cake.
Lemon curd is fantastic on this coconut cake, of course, or dolloped on a scone, on toast, or just eaten with a spoon! If you decide to just make the curd without cake follow through (but why? 😩), it will last up to two weeks in the refrigerator. As if.
In a stand mixer, mix together all the truly “dry” dry ingredients (flour, sugar, salt, baking powder) for about a minute. Add your softened butter and oil and mix on low speed until it’s the texture of wet sand and all the dry ingredients are coated in delicious fat.
Now... add coconut milk and coconut extract into the mixed dry ingredients and combine on medium speed for about one minute. There will still be some lumps in the batter, but that’s fine. They will all bake together smoothly. Trust me on this 😉
If you haven’t already done so, whip your 3 reserved egg whites in a bowl with a hand mixer until you get nice soft peaks. You should be able to (but don’t) hold the bowl upside down over your head without egg white falling on you (really, don't).
Add about 1/3 of this fluffiness into your batter and mix in well. This will “loosen” your batter a bit, so you can better fold in the rest of the whites. Add the rest of the egg whites and fold gently until fully incorporated. If there are a few white streaks left, that’s fine. We just don’t want to deflate the whites. They are going to give your cake such delightful fluffiness!
Pour the batter into an 8X8 pan (a round cake pan will work well too, as long as it’s at least 2 inches deep). Smooth the top and bake in a 350° oven for 24-28 minutes, or until a toothpick inserted in the center comes out clean. Remove from the oven and allow to completely cool on a rack.
Place the egg whites and sugar in a large metal bowl set over a pot of simmering water, making a double boiler. With the water simmering, whisk the eggs and sugar until the mixture becomes very thin and opaque (not quite clear, but clear-ish) and warm to the touch. If you have a food thermometer, it should read about 160°, which will get rid of any wee little buggers that live in raw eggs.
Remove from the heat and using a hand mixer (this is too small an amount of ingredients to use in a big stand mixer) whisk on high speed until stiff peaks are achieved. The holding a bowl over your head test works even better here. This should take about 5-7 minutes and, at the end, the sides of the bowl should be about room temperature.
On medium-low speed, begin adding the butter, one piece at a time, only adding another piece when the previous piece has been fully mixed in.
At some point in the “add the butter” process, this is gonna look like a soupy mess 😱 You are going to think that you messed up so bad that you should never be allowed to make anything harder than canned soup, ever again. Don’t spiral! It’s fine. Just keep mixing and adding butter (just keep swimming 🎶).
When all the butter is completely incorporated, you can increase the speed to medium-high. After a few minutes, everything should come together and you’ll have smooth buttercream. Add in your coconut milk and extract and mix for another minute. Done!
Once you’ve mixed it all together, if it still seems a little thin for your liking, you can put the whole bowl into the fridge for about 15-20 minutes and then mix it again for a few minutes.
I know this can seem hard and stressful, especially the first time you make it, but making Swiss meringue buttercream is easier than it sounds. It has a delicious flavor and silky texture and it never gets the hard crust on it that American buttercream does. It only took making it one time for this to become my go to frosting. It’s the one I use on almost all of my cakes and cupcakes!
Take your lemon curd and spread it in a thin layer over the top of you cooled cake. I put about 1/4 inch layer, but you might want more or less. If there is leftover curd, oh dear, I guess you’ll have to eat it 😉
Next, spread your buttercream over the layer of lemon curd. I found dropping dollops over the top of the cake and using an offset spatula to spread it was the easiest way to do this. Finally, sprinkle with a blanket of coconut flakes, in your desired thickness.
Slice, serve, and Happy Eating!