Preheat the oven to 350°F (175°C) and grease a 9×5-inch loaf pan well.

In a large bowl, combine the flour, sugar, baking powder, baking soda, and salt. Mix until evenly blended.

Add the softened butter, eggs, vanilla extract, and sour cream. Mix until the batter is smooth and fully combined.

Gently fold in the fresh blueberries, being careful not to crush them.

Pour half of the batter into the prepared loaf pan and spread it evenly.

In a separate bowl, beat the cream cheese and powdered sugar until smooth and creamy.

Spread the cream cheese mixture evenly over the batter layer in the pan.

Top with the remaining batter and smooth gently. Use a knife to lightly swirl the batter and cream cheese together.

Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean.

Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.