Preheat your oven to 350°F (175°C). Grease and flour a deep 8-inch round cake pan.

Sift together the flour, baking powder, and salt in a bowl. Set aside.

In a large mixing bowl, beat the eggs for about 1 minute. Gradually add sugar and vanilla extract, and continue beating for 7-8 minutes until thick and pale.

Gently fold in the dry ingredients in three additions, alternating with the melted butter and milk, starting and ending with the dry ingredients.

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

Remove from the oven, allow to cool in the pan for 10 minutes, then turn out onto a wire rack to cool completely.

In a mixing bowl, whip the heavy cream until stiff peaks form.

In another bowl, combine the mascarpone cheese, powdered sugar, lemon zest, lemon juice, and vanilla extract. Beat until smooth.

Gently fold the whipped cream into the mascarpone mixture until well combined.

Reserve ½ cup of this lemon cream filling for the cake's exterior.

Once the cake is completely cooled, use a long serrated knife to slice the cake horizontally into two even layers.

Place the bottom layer on a serving plate. Spread the lemon cream filling over the top, excluding the ½ cup reserved for the exterior.

Carefully place the second layer on top of the filling.

Spread the reserved ½ cup of lemon cream filling around the sides of the cake.