For the cake:

1. Preheat the oven to 350º.
2. Line the bottom of the pan with a round of parchment paper and spray the pan and parchment paper with cooking spray.
3. In a medium bowl, add the zest to the sugar and mix together.
4. In a large bowl, add the sugar to the flour mixture (flour, baking soda, baking powder, and salt). Whisk together and create a well in the center.
5. In a separate mixing bowl, combine the eggs, olive oil, juice, and Greek yogurt and whisk together until smooth.
6. Add wet ingredients to the dry ingredients and whisk or stir to combine until all dry ingredients are blended.
7. Pour batter into the prepared cake pan, place the pan in the center of the oven rack and bake for 30 minutes. You’ll know it’s done when the cake is golden brown and a cake tester is inserted into the center of the cake and it comes out clean.
8. Remove from the oven to a wire rack and let the cake cool to room temperature.
9. Transfer the cakes when cooled to a large cutting board. 
10. Make the butter cream frosting.
11. Make the candied blood orange zest (optional)
12. With a serrated knife, slice the tops of both cakes.
13. Place a small scoop of frosting in the center of your cake stand. Take one cake and place it on top of the icing with the cut side up.
14. Spread a healthy layer of butter cream frosting on the cut portion of the cake. Invert the other cake and place on top of the frosting.
15. Add a generous amount of the icing to the top of the cake, spread the frosting evenly with a few swirls, top with the candied blood orange zest if using, and serve.
16. Store the leftovers on your countertop in an airtight container or covered with plastic wrap.

For the butter cream frosting:

1. Place the butter in the bowl of a stand mixer with the paddle attachment and beat for approximately 2 minutes on low speed.
2. With the mixer running, add the confectioners’ sugar, blood orange juice, and milk and beat for another 2 minutes. Add more milk or sugar if needed to get the right consistency for easily spreading on top of the cake. 
3. Add a pinch of salt and test for taste. 

For the candied blood orange zest:

1. Add water and sugar to a small pot and bring to a simmer until the sugar has dissolved.
2. Add the zest strips to the simmering water and simmer for about 15 minutes. The zest will turn a deep, dark color.
3. With a slotted spoon, remove zest strips from water to a plate.
4. Quickly transfer the zest strips to a bowl with sugar in the bottom and toss the strips until coated with sugar.
5. Transfer the strips from the sugar to a sheet pan lined with was paper and let them fully dry (about 30 minutes)