Prepare your ingredients by gathering all necessary items and zesting the blood oranges.
Make the cake batter by mixing water, sugar, zest, olive oil, and blood orange juice, then combine with dry ingredients.
Bake the cake in preheated oven at 350°F for about 25 minutes, then cool in pans.
Prepare the buttercream by beating butter and gradually adding powdered sugar, zest, vanilla, and juice.
Create the ganache by melting dark chocolate and mixing with half-and-half until smooth.
Assemble the cake by layering the cake and frosting, then frost the entire cake.
Finish with ganache by pouring it over the frosted cake and allowing it to set.