Blood Orange Meringue Layer Cake

Preheat the oven to 175°C (350°F) with an oven rack positioned in the center.

Grease the bottoms and sides of two 20 cm (8-inch) round cake pans with butter and line the bottom of each pan with a parchment paper round.

Finely zest the navel oranges and blood oranges using a citrus zester, keeping the zest varieties separate.

Extract juice from the navel oranges, blood oranges, and lemon using a citrus juicer, keeping the juices in separate containers.

Sift the cake flour, baking powder, and fine sea salt together into a mixing bowl to aerate and eliminate lumps.

Whip whole eggs, 200g granulated sugar, and navel orange zest in a stand mixer fitted with the whisk attachment on medium-high speed for 7 minutes until pale, thick, and tripled in volume.

Fold the sifted dry ingredients into the whipped egg foam in three gentle additions using a silicone spatula until barely combined.

Whisk melted unsalted butter, warm whole milk, vanilla extract, and 50ml navel orange juice together in a mixing bowl until blended.

Gently fold the warm butter and milk mixture into the cake batter using the silicone spatula until completely uniform with no visible butter streaks.

Divide the batter equally between the prepared cake pans and bake at 175°C (350°F) for 24 minutes until golden and a wooden skewer inserted in the center comes out clean.

Cool the cake layers in their pans on a wire cooling rack for 10 minutes, then invert onto the rack, peel away parchment paper, and cool completely to room temperature.

Whisk 160ml blood orange juice, blood orange zest, 30ml lemon juice, 150g granulated sugar, whole eggs, egg yolks, and 1g fine sea salt in a heatproof bowl until fully combined.

Bring 3 cm of water to a gentle simmer in a medium saucepan over medium-low heat.

Set the heatproof bowl over the simmering saucepan and cook curd, stirring constantly with a silicone spatula, until thickened and an instant-read digital thermometer registers 80°C (176°F) to ensure egg safety.

Remove the heatproof bowl from heat and whisk in the chilled cubed butter piece by piece until fully melted, glossy, and emulsified.

Strain the warm curd through a fine-mesh sieve into a clean mixing bowl to remove citrus zest and egg chalazae.

Press a sheet of plastic wrap directly onto the surface of the strained curd and chill in the refrigerator for 2 hours until cold and set firm below 4°C (40°F).

Combine egg whites, 200g granulated sugar, cream of tartar, and 1g fine sea salt in a clean heatproof stand mixer bowl, set over the saucepan of simmering water, and whisk constantly until sugar dissolves and registers 71°C (160°F) on an instant-read digital thermometer for egg safety.

Transfer the bowl to the stand mixer fitted with the whisk attachment and whip on high speed for 8 minutes until stiff, glossy peaks form and the bowl feels cool to the touch, whipping in vanilla extract during the final minute.

Trim domed tops if needed and slice each cooled cake layer horizontally in half using a serrated cake knife to create four equal sponge rounds.

Place the bottom sponge layer on a cake turntable, spread one-third of the chilled curd evenly over the surface with an offset spatula, and repeat with remaining sponge layers and curd, finishing with the top sponge layer.

Spread the Swiss meringue generously over the top and sides of the assembled cake using an offset spatula, sculpting decorative swirls and peaks.

Caramelize the meringue exterior using a culinary kitchen torch held 5 to 7 cm away using fluid sweeping motions until the ridges turn aromatic, golden brown.

Transfer the finished cake to the refrigerator for 30 minutes to stabilize the curd layers before slicing and serving.