1. – Preheat your oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper.

2. – In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.

3. – In a large bowl, cream the butter and 1 cup of granulated sugar until light and fluffy, about 2-3 minutes. Beat in the eggs one at a time, then stir in the lemon zest and lemon juice.

4. – Gradually add the dry ingredients to the wet ingredients, alternating with the milk, mixing just until combined.

5. – Pour the batter into the prepared cake pan and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.

6. – Allow the cake to cool in the pan for 10 minutes, then invert onto a wire rack to cool completely.

7. – In a medium saucepan, whisk together the cornstarch and 1/4 cup of granulated sugar. Gradually whisk in the milk and egg yolks.

8. – Cook the custard over medium heat, stirring constantly, until thickened, about 5-7 minutes. Remove from heat and let cool completely.

9. – Once the cake and custard are both cool, use a serrated knife to split the cake horizontally into two layers.

10. – Spread the lemon custard evenly over the bottom layer, then carefully place the top layer back on.

11. – Dust the top of the cake with powdered sugar before serving.