All the citrus and berry flavors wrapped up in a moist cake with a delicious and light mascarpone cream cheese frosting. A delicious summertime treat! This is enough batter for three 6-inch cake rounds.
Preheat oven to 350°F and place the oven rack in the center position. Grease, flour and line three 6-inch round baking tins and set aside.
In a large mixing bowl, add the sugar and salt, then sift the flour and baking powder directly into the bowl. Stir with a whisk to evenly distribute all the ingredients and set aside.
In another bowl, whisk the eggs whites about 30 seconds, just to loosen them up. Add the warm milk, sour cream, vanilla paste and lemon juice. Whisk to combine.
Whisk in the butter and lemon zest until the butter looks like cottage cheese. It will not affect the bake.
Add the wet ingredients into the dry ingredients and fold to combine. Toss the berries with 1 Tablespoon of flour and fold into the batter until combined without any flour streaks. Don't over mix.
Distribute the batter evenly among the three baking tins, tap once to remove any air pockets and bake at 350°F for about 30 minutes or until golden. Test for doneness by inserting a toothpick in the center. If it comes out clean, the cake is done.
Cool in the tin for 10 minutes, then invert onto a cooling rack, remove the parchment lining and cool completely. Cover with a tea towel so they don't dry out if not assembling once cooled.
While the cake bakes, make the frosting and macerate the berries. To macerate the berries, combine and toss all the ingredients in a bowl. Let the fruit sit at room temperature for 30 minutes.
In a stand alone mixer, whip the American cream cheese for a few minutes until smooth. Add the cold mascarpone cream cheese, lemon zest and vanilla paste or extract and whip until incorporated.
Add the powdered sugar one cup at a time until blended. Remember to scrape the sides down. When all the sugar has been added, increase the speed and beat for a few minutes until light and fluffy.
In a separate bowl with a hand held mixer, whip a cup of heaving whipping cream with the cream of tartar until light and fluffy.
Using a spatula, fold a third of the whipped cream to the cream cheese mixture. Repeat process until all the whipped cream has been combined.
Place a cake layer on the cake stand. Spread an even layer of frosting on top of the cake. Any frosting that spills over the edge will be smoothed later on. Add fruit between the layers only.
Using a bench scraper or knife, even the frosting on the sides and top of the cake. Arrange the macerated fruit on top of the cake and serve. Enjoy!