1. Preheat the Oven: Begin by preheating your oven to 350°F (175°C). Prepare two 9-inch round cake pans by greasing and flouring them to prevent sticking.
2. Cream the Butter and Sugar: In a large mixing bowl, cream together the softened butter and granulated sugar until the mixture is light and fluffy. This step is crucial, as it incorporates air into the batter, ensuring a tender cake.
3. Incorporate the Eggs: Add the eggs to the creamed mixture one at a time, beating well after each addition. This helps to emulsify the mixture, creating a smooth batter.
4. Mix Dry Ingredients: In a separate bowl, whisk together the all-purpose flour, baking powder, and salt. This step not only combines these ingredients but also aerates the flour, which is essential for achieving the desired cake texture.
5. Combine Wet and Dry Ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the whole milk. This method helps maintain the structure of the batter and ensures a smooth incorporation.
6. Add Flavorings: Stir in the fresh lemon juice, lemon zest, and vanilla extract until the mixture is well combined. The acidity of the lemon juice will enhance the cake’s flavor profile while adding moisture.
7. Bake the Cakes: Divide the batter evenly between the prepared pans, smoothing the tops with a spatula. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean.
8. Cool the Cakes: Once baked, allow the cakes to cool in the pans for about 10 minutes before transferring them to a wire rack to cool completely. This resting period is vital for retaining moisture.

For the Filling:

1. Prepare the Cream: In a mixing bowl, whip the heavy cream until soft peaks form. Gradually add the lemon juice and optional lemon zest, continuing to whip until stiff peaks form. This will create a light and airy filling that complements the dense cake.

For the Icing:

1. Mix Icing Ingredients: In a separate bowl, combine the sugar, lemon juice, heavy cream, and lemon zest. Whip until it reaches a spreadable consistency, ensuring it remains smooth and creamy.

Assembly:

1. Once the cakes are completely cool, spread the lemon cream filling between the layers.
2. Ice the Cake: Apply the icing over the top and sides of the cake for a finished look.
3. Decorate: Optionally, dust the top with powdered sugar for a beautiful presentation.