If your eggs are not at room temperature, set them in a bowl of warm water now.
Preheat the oven to 350 F. Prepare a loaf pan or a 10 cup bundt pan with flour & butter or with a baking spray (I prefer the latter).
In the bowl of a stand mixer fitted with the paddle attachment, beat together the butter, sugar, zest, vanilla and salt. Beat for about 7 minutes, this mixture should be VERY light and fluffy.
Add the eggs, one at a time beating for at least a minute before adding another.
Sift the cake flour over the batter and add baking powder. Add the sour cream on top. Cover the stand mixer with a tea towel (if yours is the kind that spills) and turn the mixer on low. Beat until the flour is just incorporated.
Pour batter into the prepared cake pan. Bake for about 35-45 minutes, until you can touch the top of the cake and it springs back.
Let the cake cool for a few minutes in the pan then turn it upside down and transfer it to a plate or cooling rack.
Once it’s completely cool, make the glaze by mixing together the powdered sugar and blood orange juice: use more powdered sugar to make it thicker, more juice to thin it out.
Store in an airtight container. If making ahead of time, wait until the day of serving to make and add the glaze.