Preheat your oven to 350°F (175°C). This ensures your cake bakes evenly once it’s in the oven.
Grease your 9x13 inch baking pan with butter or line it with parchment paper for easy removal after baking.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and baking soda until well combined.
In another bowl, use an electric mixer to cream the softened butter with the sugar mixture until light and fluffy.
Gradually add the slightly beaten eggs and vanilla extract to the creamed butter and sugar, mixing until fully incorporated.
Alternately add the buttermilk and the dry mixture to the butter mixture, starting and ending with the flour. Mix until just combined; be careful not to over-mix.
Gently fold in your choice of fresh berries, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan, smoothing the top with a spatula. Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted in the center comes out clean.
Once baked, remove the cake from the oven and allow it to cool in the pan for about 10 minutes before transferring it to a cooling rack. Serve warm or at room temperature, drizzled with Berry Sauce for a touch of extra flavor.