Pre-heat oven to 350 degrees.
Line a loaf pan with parchment paper.
In a large bowl whisk butter, sugar and eggs together until smooth and creamy.
Add sour cream and mashed bananas, whisk to combine.
Mix in flour, baking soda and salt, stir until just combined.
Gently fold in frozen blueberries.
Pour into prepared loaf pan and top with sliced banana.
Bake for 1 hour or until toothpick entered into the center of the loaf comes out clean.