Preheat your oven to 350°F (175°C). Grease and flour two 9-inch round cake pans or line them with parchment paper.

1. In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
2. In a large mixing bowl, beat the softened butter and sugar together until light and fluffy, about 3-4 minutes.
3. Add the eggs, one at a time, beating well after each addition. Stir in the vanilla extract, lemon juice, and lemon zest.
4. Gradually add the dry ingredients to the wet ingredients, alternating with the milk, starting and ending with the dry ingredients. Mix until just combined.
5. Divide the batter evenly between the prepared cake pans and smooth the tops.
6. Bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.
7. For the lemon curd, whisk together the lemon juice, lemon zest, and sugar. Add the egg yolks and whisk until smooth. Place the bowl over a pot of simmering water and cook, whisking constantly, for about 8-10 minutes, until the mixture thickens.
8. Remove from heat and stir in the butter, one cube at a time, until fully melted and smooth. Add the vanilla extract and let the curd cool to room temperature. Refrigerate for at least 2 hours to set.
9. Once the cakes are completely cooled, place one cake layer on a serving plate. Spread a generous amount of lemon curd over the top of the first cake layer, leaving a small border around the edges.
10. Place the second cake layer on top and press down gently to secure. Spread more lemon curd over the top of the cake and garnish with additional lemon zest or fresh berries if desired.