Vanilla Layer Cake with Peach-Passionfruit Curd
Recipe makes one 3-layer 6” round cake (pictured in blog post) or one 2-layer 8” round cake.
INGREDIENTS
For the Peach-Passionfruit Curd (makes ~1 cup of curd; can be stored refrigerated in an air-tight container for up to a week):
2 large egg yolks (save egg whites to use in Swiss meringue buttercream – recipe below)
3 tbsp (45ml) honey or pure maple syrup
¼ C (60ml) pureed peach (from about 1 medium peach, de-skinned and pit removed)
1 tsp (10ml) fresh lemon juice
Pinch sea salt
3 tbsp (43g) unsalted butter (can substitute coconut oil or ghee)
Pulp from 2 fresh passionfruits (or about 2-3 tbsp of pulp)
For the Vanilla Swiss Meringue Buttercream (Makes ~3 cups which is just enough for naked cake look, as pictured in blog post. Double the recipe for traditional frosted cake. SMB can be made 3-4 days ahead and stored in a cool room. Extras can be frozen.):
3 large egg whites (90g)
¾ C (140g) granulated sugar
½ C + 2-3tbsp (80g) confectioner’s sugar, sifted
1 C + 2 tbsp (256g) unsalted butter, softened at room temperature 1-2 hrs or 65f
2 tsp vanilla bean paste or pure vanilla extract
Pinch sea salt
For the Gluten-Free Vanilla Cake Layers:
4 large eggs, separated
1 C (228g) unsalted butter, softened at room temperature 1-2 hrs or 65f
¾ C (140g) granulated sugar
1 1/3 C (130g) finely ground blanched almond flour (see headnotes)
2/3 C (90g) Bob's Red Mill Gluten-Free 1-to-1 Baking Flour (see headnotes)
2 tsp baking powder
Pinch sea salt
2 tsp vanilla bean paste or pure vanilla extract
Optional for garnish:
Additional peaches (sliced) and fresh passionfruits (halved)
METHOD
Prepare the Peach-Passionfruit Curd (can be stored in tight container refrigerated for up to 1 week): Heat and whisk all the curd ingredients, except the passionfruit pulp, in a small pot over low heat. Once the butter has completely melted, increase the heat to medium-low and cook 7-10 minutes or until tiny bubbles surface, all the while stirring frequently. Keep going until mixture is noticeably thickened, like thin yogurt. A thermometer should read 170f. Strain over a sieve into a bowl and stir in passionfruit pulp. The curd will thicken further as it cools, to the final pudding-like consistency of curd. Refrigerate if not using right away. Once fully cooled, check to make sure your curd is thick. If it is too thin, it may bleed through the cake layers or cause your cake layers to be less stable once stacked. Put the curd over a double-boiler again and repeat the process to cook further. Whisking in another egg yolk while you do this is also an option.
Prepare the Vanilla Swiss Meringue Buttercream (can be made 3-4 days ahead and stored in a cool room): Place both sugar and whites together in a large bowl. Over a double boiler, whisk sugar and egg whites, stirring and moving everything around constantly, until mixture reaches 115f [ update: mixture can heat up to as high as 160f ] or you can feel between your fingers that the sugar grains are completely dissolved. Pour mixture into the metal bowl of your stand mixer fitted with the whisk attachment. Whip on high speed until thick, glossy and white (very firm peaks), about 4 minutes. Meanwhile, sift confectioner's sugar. Once the egg whites are done, turn the stand mixer to the lowest speed and add the confectioner's sugar all at once. Let the whisk turn a few times to settle the sugar before increasing mixer speed to medium-high and whisking until everything is evenly incorporated. While the mixer is still running on medium-high, add the room temperature butter in 2-tbsp chunks at a time until all of it is incorporated. Add the vanilla bean paste or extract. Mix until thoroughly combined. Switch to the paddle attachment and blend on medium-low speed until the buttercream is nice and smooth, about a minute. Swiss meringue buttercream can be stored at room temperature for up to 4 days. Tip: if your Swiss meringue buttercream curdles at any point, whip the mixture on high speed for as long as it takes to get it smooth again, anywhere from 5 to 10 minutes. Quickest way is to also aim a hairdryer perpendicularly at the mixing bowl as it whips. Works like a charm every single time.
Prepare the Gluten-Free Vanilla Cake Layers: Preheat oven to 325f. Lightly grease and/or line with parchment paper, three 6” round cake pans (or two 8” round pans). Whisk the flours, baking powder and salt together and set aside. Place the butter and sugar in the mixing bowl of a stand mixer, and cream them at medium speed for 5 minutes or until light and fluffy. Separate the eggs. Add the yolks and vanilla to the butter-sugar mixture and beat a minute more. Add the flour mixture all at once and beat on low until just mixed. Transfer batter to new bowl and clean the stand mixer bowl very thoroughly with soap and wipe dry. Whip egg whites to soft peaks. Fold whites into cake batter. Divide batter evenly amongst prepared cake pans. If you are making three 6” cakes, bake them for 25-30 minutes, or until a skewer pierced into the middle emerges clean with just a crumb or two. If you are bake two 8” cakes, bake for 50-60 minutes or until a skewer emerges clean with just a crumb or two. Since ovens vary widely, it is always a good idea to check doneness earlier to ensure cake does not over-bake. Over-baking will surely result in dry cake. Cool cakes in their pans for 5 minutes on a wire rack, then remove the cakes and cool fully. Make sure cakes are fully cooled before frosting.
Assemble the Cake: Scoop some of the buttercream into a piping bag and snip off the end for ¾” opening – you just need to eyeball enough to pipe rings around the edge of the inside layer(s) to encircle the curd. Place bottom cake layer on your cake stand or serving plate. Scoop about ½ cup of buttercream for 6” cake (more for 8” cake) and spread evenly with spatula. Pipe a ring of buttercream around the edge. Fill center of the ring with fully cooled peach-passionfruit curd, about ¼ cup for a 6” cake layer, more for 8”. Place next cake layer on top, upside down so the flat bottom is facing upward. Repeat one more time for a three-layered cake, placing final cake layer upside down again so the flat cake bottom is facing upward. Frost top and outside of cake with a thin layer of buttercream, filling in the outside in between the layers as needed and smoothing the buttercream with a spatula or icing smoother. This is the crumb coat. Refrigerate 15 minutes. Frost entire cake with remaining buttercream, this time taking more care for a smooth finish. Garnish the cake with fresh peaches, fresh passionfruit curd and flowers or petals if you like. I used Dahlias.