Preheat oven to 350 degrees. Spray a loaf pan with cooking spray. Set aside.
In a small bowl, combine the flour and baking soda. Set aside.
In the bowl of a standing mixer, cream the butter and sugars at medium speed for 2 minutes.
Add the orange zest, orange juice, eggs and vanilla bean paste and continue beating for another minute.
Reduce mixer speed to low, add the flour and baking soda to the butter mixture and mix until combined, scraping down the sides as needed.
Add the chia seeds and sour cream and mix until just combined.
Pour the batter into the prepared loaf pan. Garnish with sliced blood oranges (optional).
Bake for 55 - 60 minutes or until a toothpick inserted into the middle comes out clean.