Blood Orange Cake Doughnuts

Name: Blood Orange Cake Doughnuts
Prep time: 15 min
Cook time: 10 min
Total time: 25 min
Cuisine: American
Ingredients: 1 tablespoon blood orange zest; 2/3 cup granulated sugar; 8 tablespoons Kerrygold Unsalted Butter (softened, 113 g); 2 eggs (room temperature); 1/2 cup whole milk (room temperature, 120 g); 1/4 cup full fat sour cream (room temperature, 60 g); 2 teaspoons pure vanilla extract; 2 3/4 cups unbleached all purpose flour (330 g); 2 teaspoons baking powder; 1/2 teaspoon baking soda; 1/2 teaspoon kosher salt; 1/4 cup blueberries; 1 tablespoon sugar; 3 cups powdered sugar (390 g); Juice of 2 blood oranges; pinch of kosher salt; 5-6 cups neutral oil (for frying)