Prepare the Lemon Curd

 

1. Separate the yolks from the whites. Set aside the egg whites for the Swiss meringue buttercream.
2. In a small saucepan, combine 1 cup of sugar and lemon zest. Massage the zest into the sugar.
3. Add in 6 egg yolks and whisk until the mixture lightens in color. Mix in lemon juice.
4. Heat on medium-low, stirring constantly until the mixture thickens and bubbles.
5. Remove from heat, add butter, and mix until melted. Strain into a bowl and set aside to cool.

2. Make the Lavender Milk

 

1. Heat 1 cup of milk in a saucepan until it begins to simmer. Remove from heat.
2. Add dried lavender and let steep for 15 minutes. Strain and cool.

3. Bake the Cake Layers

 

1. Preheat oven to 350°F (175°C). Prepare three 8-inch or four 7-inch cake pans.
2. Combine sugar and lemon zest in a large bowl, massaging the zest into the sugar.
3. Add cake flour, baking powder, and salt. Mix in butter on low speed until mixture resembles moist sand.
4. Add egg whites, sour cream, lavender milk, oil, and vanilla. Mix on low speed until combined.
5. Divide batter into two bowls, color one purple and the other yellow. Swirl colors together in pans.
6. Bake for 33-36 minutes. Cool in pans for 10 minutes, then transfer to wire racks.

4. Prepare the Frosting

 

1. Clean your mixing bowl. Heat egg whites and sugar over simmering water until 160°F (71°C).
2. Transfer to stand mixer, whip until stiff peaks form. Add butter one stick at a time.
3. Mix in lavender milk, vanilla, and salt. Continue mixing until smooth.

5. Assemble the Cake

 

1. Stack and frost cake layers with a thin layer of buttercream and a ring of frosting filled with lemon curd.
2. Chill the cake, then apply a crumb coat and chill again.
3. Apply a final layer of frosting and add colorful swipes with reserved frosting.