1. Preheat the oven to 350°F (175°C).

2. In a large mixing bowl, cream together the butter and sugar until light and fluffy.

3. Add the eggs one at a time, mixing well after each addition.

4. Stir in the vanilla extract.

5. In a separate bowl, combine the flour, baking powder, and salt.

6. Gradually add the dry ingredients to the wet mixture, alternating with the milk, and mix until just combined.

7. Pour the batter into a greased 9×13 inch baking pan.

8. Bake for 25-30 minutes or until a toothpick inserted in the center comes out clean.

9. Let the cake cool completely.

10. Once cooled, spread whipped cream on top and arrange the red berries and blueberries in a flag pattern.