Preheat oven to 350 degrees. Place cupcake liners in muffin tins or grease each muffin tin.
Place the butter, cream cheese and sugar in a large bowl, beat until creamy. Add the eggs one at a time beating well after each addition. Add the vanilla, beat until incorporated.
In a medium bowl, combine the flour,baking powder and salt, stir to combine. Stir the flour mixture into the butter mixture just until moistened. Fold the blueberries and pecans into the batter. Fill muffin liners 3/4 full with batter, bake 20 - 25 minutes or until a toothpick inserted comes out clean. Cool in the muffin tins five minutes before removing to cool completely on wire racks.