Creating the Fluffy Lemon Custard Cake is a joyful process that can be easily accomplished by following these steps:

1. Preheat Oven: Preheat your oven to 350°F (175°C) and grease an 8-inch round cake pan.

2. Prepare Dry Ingredients: In a bowl, whisk together the flour, baking powder, and salt. Set this mixture aside.

3. Beat Butter and Sugar: In another bowl, cream the softened butter and granulated sugar together until light and fluffy.

4. Add Eggs: Beat in the eggs one at a time, ensuring they are fully incorporated after each addition.

5. Mix Lemon and Vanilla: Add the lemon zest, lemon juice, and vanilla extract to the egg mixture, mixing until well combined.

6. Combine Ingredients: Gradually add the dry ingredient mixture to the wet mixture, alternating with the whole milk. Stir until just combined, making sure not to overmix.

7. Pour Batter: Pour the batter into the prepared cake pan and smooth the top.

8. Bake: Bake in the preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean.

9. Cool the Cake: Remove from the oven and let it cool in the pan for 10 minutes. Then transfer to a wire rack to cool completely.

10. Prepare Whipping Cream: In a separate bowl, whip the heavy cream with powdered sugar until soft peaks form.

11. Assemble the Cake: Once the cake is completely cooled, slice it in half horizontally. Spread half of the whipped cream on the cut side of the bottom layer, then place the top layer back on.

12. Top with Remaining Cream: Spread the remaining whipped cream over the top of the cake.

13. Garnish: Decorate with fresh lemon slices or lemon zest if desired.

14. Chill and Serve: Let the cake chill in the refrigerator for about 30 minutes before serving to firm up the whipped cream.

Following these steps will help you create a Fluffy Lemon Custard Cake that is not only visually appealing but also incredibly tasty!