Preheat oven to 350°F (177°C). Grease and flour two 8-inch (20-cm) round cake pans. Mix flour, baking powder, and salt in a bowl.
In another bowl, cream butter and sugar until fluffy. Add eggs one at a time, mixing well. Stir in vanilla.
Alternate adding dry ingredients and milk, starting and ending with dry ingredients.
Divide batter between pans and smooth tops. Bake for 25–30 minutes or until a toothpick comes out clean. Cool completely on wire racks.
Toss berries with lemon juice and sugar. Let sit for 10 minutes to macerate.
Beat chilled cream, powdered sugar, and vanilla until stiff peaks form.
Place one cake layer on a plate. Spread whipped cream, then layer with half the macerated berries.
Repeat with the second cake layer. Top with more cream and berries. Garnish with extra berries and mint if desired. Chill for 1 hour before serving.