Ingredients:

  • 2 ½ cups (315 g) All-Purpose Flour, sifted
  • 1 ¾ cups (350 g) Granulated Sugar (Caster)
  • 1 Tbsp (15 g) Baking Powder
  • ½ tsp (3 g) Salt (Fine sea salt)
  • 1 cup (225 g) Unsalted Butter, softened, room temperature
  • 4 Large Eggs, room temperature
  • 1 cup (240 ml) Buttermilk, full fat
  • 2 tsp (10 ml) Pure Vanilla Extract
  • 1 Tbsp Orange Zest (from 2 large oranges)
  • 6 Large Egg Yolks (for Curd)
  • ¾ cup (150 g) Granulated Sugar (for Curd)
  • ¾ cup (180 ml) Fresh Orange Juice, strained (for Curd)
  • 1 tsp Orange Zest (for Curd)
  • ½ cup (115 g) Unsalted Butter, cut into cubes, cold (for Curd)
  • ½ cup (120 ml) Fresh Orange Juice (for Syrup Soak)
  • ¼ cup (50 g) Granulated Sugar (for Syrup Soak)
  • 5 Large Egg Whites (150 g) (for SMB)
  • 1 ½ cups (300 g) Granulated Sugar (for SMB)
  • 1 ½ cups (340 g) Unsalted Butter, cold, cubed (for SMB)
  • 1 tsp (5 ml) Pure Vanilla Extract (for SMB)
  • ½ tsp (2.5 ml) Orange Extract (optional but recommended)

Instructions:

  1. Prepare the Orange Curd: Whisk egg yolks, sugar, orange juice, and zest in a medium saucepan. Cook over medium-low heat, stirring constantly, until the mixture coats the back of a spoon (reaching 180°F/82°C). Do not boil.
  2. Emulsify Butter & Chill Curd: Remove the curd from heat and whisk in the cold butter cubes, one at a time, until completely smooth. Strain the mixture through a fine-mesh sieve. Cover the surface directly with plastic wrap and chill for at least 3 hours until firm and spreadable.
  3. Bake the Sponge (Preheat & Cream): Preheat oven to 350°F (175°C). Grease and line three 8-inch tins. In the stand mixer, cream the softened butter, sugar, and orange zest until pale and fluffy (3–4 minutes). Add eggs one at a time, beating well after each, then mix in the vanilla.
  4. Combine Wet/Dry: Whisk flour, baking powder, and salt together. Alternately mix the flour mixture and the buttermilk into the wet ingredients, starting and ending with the dry. Mix only until just combined. Divide batter evenly and bake for 28–32 minutes. Cool completely on a wire rack.
  5. Prepare the Orange Syrup Soak: Combine orange juice and sugar in a small saucepan. Bring to a simmer until sugar is dissolved. Remove from heat and let cool slightly before use.
  6. Make the Swiss Meringue Buttercream (SMB Base): Combine egg whites and sugar in the mixer bowl. Place over simmering water (bain-marie), whisking constantly until the mixture reaches 160°F (71°C) and the sugar is dissolved. Whip on high speed until stiff, glossy peaks form and the bowl is cool to the touch (8–10 minutes).
  7. Finish Frosting: Switch to the paddle attachment. Add the cold cubed butter slowly while mixing on low speed. Increase speed and mix until the mixture snaps back into a smooth, creamy frosting. Beat in the vanilla and orange extract.
  8. Assemble (Soak & Fill): Level the cooled cake layers. Brush each layer generously with the slightly warm orange syrup. Place the first layer on the serving plate, pipe an SMB dam around the edge, and fill the center with half of the chilled orange curd. Repeat with the second layer, then top with the final layer.
  9. Crumb Coat & Final Frosting: Apply a very thin layer of SMB (the crumb coat) over the entire cake. Chill for 30 minutes. Apply the remaining frosting smoothly around the cake. Decorate as desired and keep chilled until 30 minutes before serving.