This vanilla bean blood orange cake is frosted with a simple blood orange buttercream, and it's finished with a vanilla bean blood orange glaze and candied blood oranges! It's the perfect winter citrus cake and many components can be made ahead of time!
Make the candied blood oranges. Combine sugar, water, and corn syrup in a medium pan. Bring to a boil, reduce heat, and simmer until sugar is dissolved, about 3 minutes. Add the orange slices in 1 layer and simmer until transparent, about 1 hour. Using a slotted spoon, letting excess syrup drip off, transfer the oranges slices to a wire rack to cool completely.
Preheat oven to 350℉. Grease and flour three 8'' cake pans and line the bottoms with parchment paper. Set aside.
In a medium mixing bowl, combine the flour, baking powder, baking soda, and salt. Whisk to combine and set aside. In a large mixing bowl, combine the eggs, granulated sugar, and brown sugar and whisk until smooth. Add the butter, vanilla, vanilla bean seeds, blood orange zest, sour cream, and milk and whisk until combined.
Add the dry ingredients to the wet and mix with a rubber spatula until just combined. Pour the batter evenly into the pans and smooth out the tops with a spatula. Bake for 22-25 minutes or until a toothpick inserted comes out clean. Let the cakes cool for 10 minutes, then remove them from the pans and let cool the rest of the way on a cooling rack.
Make the frosting. Add the butter to the bowl of a stand mixer and whip on medium high for 2-3 minutes until light and fluffy. Reduce speed to low and gradually add the powdered sugar until combined. Add the vanilla and half of the blood orange juice and increase speed to medium-high and whip for 2-3 minutes. Add the remaining blood orange juice and whip for another 2-3 minutes or until super fluffy.
To make the glaze, combine the powdered sugar, vanilla bean seeds, blood orange juice, and salt in a medium bowl and whisk until smooth. If it seems too thick, add another tablespoon of orange juice, and if it seems too thin, add powdered sugar until desired consistency is reached.
To assemble the cake, place one layer on a plate or the cooling rack (just so you don't mess up the plate you are serving on, or the cake stand!), and spread the top with the frosting. Top with another layer and spread top with frosting. Top with the third layer and spread with another layer of frosting, leaving a little bit left for the sides of the cake. Use the leftover frosting to "half" frost the sides, to create a "semi-naked" effect. Use an offset spatula or bench scraper to smooth out the sides of the cake. Pour the glaze over the cake and let it drip down the sides. Garnish with the candied blood orange slices!