Preheat your oven to 335°F (170°C) and grease three 8-inch round cake pans.

In a stand mixer, combine cake flour, sugar, baking powder, and salt. Add softened butter and mix until crumbly.

In a separate bowl, whisk together eggs, buttermilk, and vanilla. Gradually add to dry ingredients while mixing until smooth.

Divide batter among prepared pans and bake for approximately 30 minutes. Cool in pans for 10 minutes before transferring to racks.

Once cooled, level cake tops with a serrated knife.

In a large bowl, whisk mascarpone, sugar, and vanilla until smooth. Whip heavy cream until stiff peaks form and fold into mascarpone mixture.

Make simple syrup by combining sugar and water, adding berry jam for flavor. Heat until sugar dissolves and cool.

Assemble the cake by layering cake, syrup, frosting, and fresh berries. Repeat for each layer and frost the top and sides.

Decorate the top with additional fresh berries before serving.