Preheat the oven to 375°F (190°C). Line a 12-cup muffin tin with paper liners.
In a large bowl, whisk together the all-purpose flour, 3/4 cup granulated sugar, baking powder, baking soda, and salt.
In a separate medium bowl, whisk the melted butter, buttermilk, eggs, and 1 teaspoon vanilla extract until combined.
Pour the wet ingredients into the dry ingredients and gently fold together until just combined. Do not overmix.
Fold in the fresh blueberries carefully to avoid breaking them.
In a small bowl, beat the softened cream cheese with 1/4 cup granulated sugar and 1/2 teaspoon vanilla extract until smooth and creamy.
Fill each muffin cup about one-third full with the blueberry batter.
Add about one tablespoon of the cream cheese mixture into the center of each muffin cup.
Top each muffin cup with the remaining blueberry batter, filling about two-thirds full.
Bake for 22 to 25 minutes, or until a toothpick inserted into the muffin (avoiding the cream cheese center) comes out clean and the tops are golden brown.
Remove from the oven and allow the muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.