01 -
Preheat oven to 350°F. Grease and flour three 6-inch cake rounds and line with parchment.
02 -
In a medium bowl, whisk flour, baking powder, and salt until well combined. Set aside.
03 -
Using a stand mixer fitted with a paddle attachment, cream butter and lemon zest until smooth. Add sugar and beat on medium-high speed until pale and fluffy, approximately 3 minutes.
04 -
Reduce speed and add eggs one at a time, fully incorporating after each addition. Add vanilla extract.
05 -
Alternate adding the flour mixture with milk and lemon juice, beginning and ending with the flour. Make 3 additions of the flour mixture and 2 of the milk and lemon juice. Fully incorporate after each addition.
06 -
Spread batter evenly between the prepared pans and smooth the tops. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out mostly clean.
07 -
Place cake layers on a wire rack to cool for 10 minutes, then turn them out onto the wire rack to cool completely.
08 -
Place eggs and sugar into a small pot and whisk to combine. Add lemon juice, zest, and butter. Cook over medium-low heat, whisking constantly, until the mixture thickens and coats the back of a spoon. Transfer to a bowl and lay plastic wrap directly on the surface to prevent a skin from forming. Chill for 2 hours to set.
09 -
In a medium saucepan, whisk together sugar, flour, and salt. Add milk and vanilla, stirring to combine. Cook over medium heat, stirring constantly, until the mixture boils. Continue cooking for 1-2 minutes until thickened to a pudding consistency. Remove from heat and let cool to room temperature.
10 -
Using a mixer, beat the room temperature butter on high speed until pale and fluffy, roughly 3 minutes. Gradually add the cooled flour mixture one tablespoon at a time, mixing well after each addition. Beat for an additional 2-3 minutes until smooth and fluffy.
11 -
Place one cake layer on a serving plate. Poke holes with a skewer and drizzle with simple syrup if desired. Spread a thin layer of buttercream and pipe a border around the edges to hold the lemon curd. Fill with 1/3 of the lemon curd. Repeat this process with the remaining cake layers.
12 -
Apply a crumb coat of frosting to the assembled cake and chill for 20 minutes. Frost the cake completely and smooth it with an icing scraper. Pipe rosettes with the remaining frosting and top with the remaining lemon curd. Decorate with thin slices of lemon and lemon zest as desired.