Preheat your oven to 350°F (175°C) and prepare a 9x5-inch loaf pan by greasing it or lining it with parchment paper.

In a large bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. In another bowl, beat the unsalted butter and granulated sugar until fluffy. Incorporate the eggs one at a time, then stir in the vanilla. Gradually mix in the dry ingredients with the milk, alternating between them, and gently fold in the blueberries until just combined.

In a separate bowl, beat the cream cheese, sugar, egg, and vanilla extract until smooth and creamy, ensuring there are no lumps.

Pour half of the blueberry batter into the prepared loaf pan, add a layer of the cream cheese filling, then top it with the remaining batter, ensuring even coverage.

Place the loaf pan in the preheated oven and bake for 55-65 minutes. Check for doneness with a toothpick; it should come out clean. If the top starts to brown too quickly, cover with aluminum foil.

Once baked, allow the bread to cool in the pan for about 10 minutes before transferring it to a wire rack. Let it cool completely before slicing to maintain a nice texture.