Prepare the oven and loaf pan:
Preheat your oven to 350°F (175°C). Grease and flour a 9×5-inch loaf pan or line it with parchment paper.

Make the bread batter:
In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, cream together the softened butter and granulated sugar until light and fluffy. Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients, alternating with the milk (or buttermilk), mixing just until combined. Be careful not to overmix.

Toss the blueberries in 1 tablespoon of flour to prevent them from sinking to the bottom of the bread. Gently fold the flour-coated blueberries into the batter.

Prepare the cream cheese filling:
In a separate bowl, beat together the softened cream cheese, granulated sugar, egg, and vanilla extract until smooth and well combined.

Assemble the bread:
Pour half of the bread batter into the prepared loaf pan. Spread the cream cheese filling evenly over the batter. Then, add the remaining bread batter on top of the cream cheese filling, smoothing the top with a spatula.

Bake the bread:
Bake for 55-65 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs. If the top starts to brown too quickly, cover the bread loosely with foil and continue baking.

Cool and serve:
Allow the bread to cool in the pan for 10-15 minutes, then transfer it to a wire rack to cool completely. Slice and serve!