Preparation Steps

• Preheat the oven to 350°F (175°C). Grease and flour two 8-inch round cake pans and line the bottoms with parchment paper.
• In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
• In the bowl of a stand mixer, cream the butter and granulated sugar on medium-high speed until light and fluffy, about 3 to 4 minutes.
• Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and lemon zest.
• With the mixer on low, add the dry ingredients in three additions alternating with the milk, beginning and ending with the dry ingredients. Mix until just combined.
• Fold in the 0.5 cup lemon juice gently into the batter. Divide the batter evenly between the prepared pans and smooth the tops.
• Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out clean. Cool in the pans for 10 minutes, then turn out onto a wire rack to cool completely.
• Make the lemon curd filling: In a heatproof bowl, whisk together 3 eggs, 0.75 cup sugar, and 0.5 cup lemon juice. Cook over a double boiler or in a saucepan over low heat, stirring constantly, until thickened to a curd (about 6 to 8 minutes). Remove from heat and whisk in 0.25 cup butter until smooth. Cool to room temperature.
• Make the lemon butter frosting: Beat 1.0 cup softened butter until smooth, then gradually add 3.0 cups sifted powdered sugar on low speed. Add 2 tbsp lemon juice, 2 tbsp heavy cream, and 1 tsp vanilla; beat on medium-high until light and fluffy. Adjust consistency with more cream if needed.
• Assemble the cake: Place one cake layer on a serving plate, spread the cooled lemon curd evenly over the layer, then top with the second cake layer. Apply a thin crumb coat of frosting, chill 15 minutes, then finish frosting the cake. Garnish with extra lemon zest if desired.