Preheat your oven to 350°F (175°C) and grease two 8-inch round cake pans, lining the bottoms with parchment paper.

In a mixing bowl, sift together the all-purpose flour, baking powder, and salt.

In another bowl, beat the eggs and granulated sugar until pale and fluffy, about 5 minutes, then mix in vanilla extract and lemon zest.

Gently fold the dry ingredients into the egg mixture until just combined, then divide the batter between the prepared pans.

Bake for 18-20 minutes until golden, and a toothpick comes out clean. Allow the cakes to cool completely.

In a small saucepan, combine water, granulated sugar, and limoncello over medium heat, stirring until the sugar dissolves, around 3-4 minutes. Let cool.

In a large mixing bowl, combine the mascarpone cheese, powdered sugar, lemon juice, and vanilla extract. Beat until smooth, about 2-3 minutes.

In a separate bowl, whip the heavy cream until soft peaks form. Fold into the mascarpone mixture.

Slice each cooled cake horizontally in half to create four layers. Brush layers with limoncello syrup and spread mascarpone filling between each layer.

Chill the assembled cake in the refrigerator for at least 1 hour to meld flavors.

Drizzle the remaining limoncello syrup over the top layer, dust with powdered sugar, and garnish with lemon slices and mint.