Preheat oven to 350°F. Spray (2) tiara pans with no stick cooking spray.
In a large mixing bowl, combine cake mix, water, oil, and eggs. Beat with an electric mixer on medium speed for 2 minutes.
Divide batter evenly between prepared pans. Tap pans gently on the counter to remove air bubbles.
Bake 17–18 minutes, or until lightly golden and a toothpick inserted in the center comes out clean.
Cool for about 10 minutes, then carefully invert onto a wire rack. Allow cakes to cool completely.
Transfer the cake to a serving plate. Prepare the filling by beating mascarpone cheese, confectioner’s sugar, and vanilla until smooth. Spread into the center indentation of the cake. Refrigerate for 30 minutes.
Prepare whipped cream by beating heavy cream and confectioner’s sugar on high speed until stiff peaks form. Refrigerate until ready to use. Pat the cleaned strawberries dry if needed.
Arrange strawberries over the filling in a decorative pattern. Pipe or spoon whipped cream around the edges of the cake.
Keep cake refrigerated until ready to serve.