This cake features in-season blood oranges in both the batter and in an upside down layer. The whole fruit is pulverized into a purée which is folded into the batter. A second orange, thinly sliced, is layered on the bottom of the pan much as if making an upside down cake. I used a citrus flavored olive oil in my batter to add a triple punch of citrus flavor. This is a moist cake with bold bittersweet notes as the whole fruit, pith and peel included, is used. If you love marmalade, you will love the bite of citrus in this cake.