Preheat oven to 350°F (175°C). Grease and line three 8-inch pans with parchment paper.
Mix dry ingredients: In a bowl, whisk together flour, baking powder, baking soda, and salt.
Cream butter and sugar: In another bowl, beat butter and sugar until light and fluffy.
Add eggs and vanilla: Beat in eggs one at a time, then mix in vanilla extract.
Combine: Alternate adding dry ingredients and buttermilk, mixing until smooth.
Bake: Divide batter evenly between pans. Bake 25–28 minutes or until a toothpick comes out clean.
Cool: Let cakes cool for 10 minutes, then transfer to a wire rack to cool completely.
Prepare frosting: Beat cream cheese and mascarpone until smooth. Gradually add powdered sugar, vanilla, and almond extract. Whip in heavy cream until fluffy.
Prepare berry filling: Toss mixed berries with lemon juice and a little sugar (optional).
Assemble: Place one cake layer on a plate, spread frosting, add berries. Repeat layers.
Frost: Cover entire cake with chantilly frosting.
Decorate: Top with more fresh berries. Chill for 1 hour before serving.