Looking in the store for inspiration, I saw that key limes were inexpensive. I love key limes, so I decided a key lime curd would be awesome as filling in the cake. I adapted this recipe for my curd.
The frosting is a vanilla lime Swiss butter cream. It is flavored with a little key lime zest, and some vanilla extract.
To garnish the cake, I candied some key lime slices in a simple syrup.
I really like this cake. This recipe is a keeper. The cake is not as fluffy as the chiffon cake I learned to make in school. It still has a very tender crumb, and there is definitely a bit of buttermilk tang to the flavor. It is a sturdier cake, and would hold up to more manipulation, if one was inclined to do something interesting with the construction.
I am very pleased with this cake. It is firm, but still moist and tender. I like the intensity of the curd. I think it's acidity helps cut the sweetness, and that plus the buttermilk helps give depths and complexities of flavor. The lightly flavored butter cream frosting complements, without overshadowing, the cake.
Buttermilk Chiffon Cake3 cups cake flour
1 tsp. baking soda
1/2 tsp. salt
1 cup shortening
1 1/2 + 1/2 cups sugar
1 cup buttermilk
1/2 tsp. almond extract
6 oz. by wt. egg whites
1 tsp. cream of tartar
Pre-heat oven to 350 F.
Grease and flour two nine inch round cake pans. Line bottoms with wax or parchment paper.
Sift together flour, baking soda, and salt. Set aside.
In the bowl of a stand mixer, cream together shortening and 1 1/2 cups sugar until light and fluffy. Add flour mixture in stages, alternating with buttermilk. Beat to combine thoroughly between each addition.
Beat egg whites until foamy. Add almond extract and cream of tartar. Whip to soft peaks, then slowly add 1/2 cup sugar. Whip to medium stiff peaks.
Fold 1/4 of egg whites into batter to lighten. Gently fold in remaining whites, until whites and batter are well combined, with no visible streaks of whites remaining.
Divide batter between cake pans.
Bake 25 - 30 minutes, or until cake is firm. Remove to rack to cool.
Key Lime Curd1 cup sugar
4 eggs, beaten
1/2 cup fresh squeezed key lime juice
2 Tbsp. key lime zest
pinch kosher salt
Combine all ingredients in a small sauce pan over medium low heat. Cook, whisking constantly, until curd thickens, about ten minutes.
Strain curd. cover surface with plastic wrap to prevent a skin from forming. Chill in freezer for 20 minutes, then transfer to refrigerator to finish cooling.
Vanilla Lime Swiss Butter Cream Frosting
6 oz by wt. sugar
4 1/2 oz by wt. egg whites
1 Tbsp. + 2 tsp. water
1 lb. butter cut into 1/2 inch cubes
1 tsp. vanilla extract
zest of one key lime
1/4 tsp. kosher salt
Heat sugar, egg whites, and water in a double boiler to 160 F, whisking continuously. Whip in a stand mixer five minutes, or until mixture decreases to room temperature. Add butter one chunk at a time, until all the butter is Incorporated. Add salt, vanilla, and lime zest. Whip until smooth and glossy.