Preheat the oven to 350°F (175°C). Grease and flour a 9x5-inch loaf pan.
In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, beat the butter and sugar together until light and fluffy.
Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.
Gradually add the flour mixture, alternating with sour cream, until fully combined.
Fold in the strawberries and blueberries gently.
Pour the batter into the prepared loaf pan and smooth the top.
Bake for 55-65 minutes, or until a toothpick inserted in the center comes out clean.
Let the cake cool in the pan for 10 minutes before transferring to a wire rack to cool completely.
Slice and enjoy!