2. Make the lemon curd:
In a small saucepan, whisk together egg yolks, sugar, lemon juice, and lemon zest.
Cook over medium heat, stirring constantly, until the mixture thickens enough to coat the back of a spoon (about 6–8 minutes).
Remove from heat and stir in butter until smooth.
Let cool completely before using.

3. Make the frosting:
In a large bowl, beat butter until creamy.
Gradually add powdered sugar, lemon juice, heavy cream, and vanilla extract.
Beat for 3–4 minutes until light and fluffy. Add food coloring if desired.

4. Assemble the cake:
Place the first cake layer on a serving plate or cake stand. Spread a thin layer of frosting, then a layer of lemon curd.
Add the second cake layer and repeat with frosting and lemon curd.