There is something about summer that screams LEMON. Perhaps it is all the lemonade we drink at our barbecues? I'm not sure about the instinct, given lemons and limes are readily available year round, but when May rolls in suddenly my chocolate cravings cease and I'm ready to dive into all things lemon. May also seems an apt time to start turning all your baked goods into rainbows, given the beautiful bows that grace the sky. And then, I came across a cheap bag of red oranges and some grapefruit and suddenly the idea for this cake popped into my head.
The cake itself is white and well, glorious. I was looking for a recipe that would give me something light and fluffy and BraveTart's White Mountain Cake promised to do both. Stella's genius idea in this cake is to add coconut oil which keeps the cake very moist. A few things about the cake, you don't want to over-beat it and you do want your eggs, buttermilk and butter at room temperature before you start. I found that it came together like a dream, as did her swiss meringue buttercream which I've raved about elsewhere. To bring that citrus power into all parts of the cake I filled the layers with lemon curd using Ina Garten's absolutely delicious recipe and added lemon juice and zest to my buttercream.
While the cake and design may signify spring/summer season, the beauty of this cake is that you can make it anytime since most citruses are available year-round. If blood oranges are difficult to find I would use a regular orange and make it the third from the bottom to get that pretty rainbow effect.
Four Layer Citrus Cake
Ingredients for Four Citrus Cake
1 stick butter, at room temperature
1/3 cup coconut oil
8 oz sugar (1 cup plus 1/8 cup)
1 1/8 tsp baking powder
1 1/4 tsp baking soda
heaped 1/4 tsp salt
4 egg whites
1/2 Tablespoon of vanilla
1 cup butermilk
2 cups cake flour
zest of half a blood orange, plus 1 tablespoon juice from the blood orange
zest of a half a lemon, plus 1 tablespoon juice from the lemon
zest of 1 lime, plus 1/2 tablespoon juice from the lime
zest of half a grapefruit, plus 1 tablespoon juice from the grapefruit
gel food coloring (green, yellow, pink, and a dark red)
Begin by making the buttercream and lemon curd. These can be made hours or even days ahead of time and stored in the fridge. If they are in the fridge, you'll need your buttercream to come to room temperature and to fluff it again before you use it. Next, make the cakes:
Preheat oven to 325, butter and flour two 5 inch cake pans.
In the bowl of a stand-mixer combine butter, coconut oil, sugar, baking powder, baking soda, and salt (you can also use a hand mixer). Mix on low speed to moisten then increase to medium and cream until light and fluffy (scrape your bowl halfway).
Add egg whites one at a time while mixer is running. Add vanilla and combine.
Reduce the speed to low and add the cake flour and buttermilk in halves, alternating between them.
Once smooth, mix with a spatula or spoon to ensure the ingredients on the bottom are combined.
Divide your batter into four bowls. Into the first bowl add the lime and its zest, and just enough green food coloring to make a pale color. Into the second, add the lemon juice and zest (if the batter looks yellow enough, leave it as is - otherwise use a tad yellow coloring to turn it yellow). Bake your first two cakes for 25 - 30 minutes, checking at 25 minutes for doneness.
To the third bowl add the grapefruit zest and juice, add some pink color and a drop or two of yellow to get as close as possible to the grapefruit color. To the fourth, add the blood orange zest and juice. The blood orange lends itself to a lovely color alone but should you wish to deepen it, use the red and pink to get you closer to the real color.
Once your first two cakes come out, let them cool for 5 minutes then remove and place on cooling rack. Wash the pans, dry them and butter and flour them. Bake your last two cakes the same way.
Once all your cakes are done and cool, trim the domes off with a bread knife. Begin layering with the green on the bottom (bottom down), and using a piping bag, pipe a circle border around the edge of the cake. Fill with lemon curd. On top, place your lemon cake face down. Repeat process until you have the blood orange on top, face down. Frost the whole cake with buttercream.
To my buttercream I added a the zest of a full lemon and about 1/2 tablespoon of its juice. This made for a wonderfully tangy buttercream and brought the citrus flavor full circle.
You need not use any food coloring if you don't want to. The lime zest will show up in tiny flecks once baked as will the blood orange zest. The blood orange juice will also color your batter slightly. For deeper effects, I used the coloring gel.
I cut all the original recipes in half - this made for a perfect fit for my cakes. I ended up with a ton of leftover lemon curd (oh the horror... ;-) ) and since I only did a crumb coat on my cake, I had some leftover frosting. If you were to frost fully, I believe it would be exactly enough. If you wanted to make a cake that serves 8-12 people, make the full buttercream recipe, half the lemon curd (unless your want those leftovers!) and double the cake recipe you see here. Stella says to use three 8X3 cake pans and to bake for 40 minutes.
Feel free to add more/less zest to each part of the cake depending on how strong you want the flavor. Juice will bring the flavor as well but don't add more than 1 TB to each part or the cake liquid ratio might be too much.
Stella is very particular about the temperature of the buttermilk, butter and egg whites: she says to use them when they are between 65-70 degrees F. To get to this temperature she suggests microwaving in 6 second bursts and checking the temperature.