Take four of the Moro blood oranges, and add them, whole – skins and all – to a saucepan. Cover with water and bring to a boil over a medium-high temperature.
Add water if necessary to keep fruit submerged.
Simmer until fruit is tender – up to two hours.
Drain the water and allow the fruit to cool.
Once cool, cut the oranges in half. Take out any seeds you can find.
Add the oranges to a blender or food processor and blend until smooth (including skin).
Pre-heat the oven to 350°F. Use a little oil to grease a 9-inch cake pan. Line it with baking paper.
Add 1 cup fine sugar, ground almonds, fennel, vanilla seeds, baking powder, and salt to a bowl. Mix together.
Add the blood orange puree and beaten eggs. Stir together until the batter is well blended.
Pour into cake pan and bake for 50 to 60 minutes. A skewer should come out clean.
Juice the last two Moro blood oranges into a small saucepan.
Add the lemon juice and last 1/4 cup sugar to the saucepan.
Heat over a low temperature, stirring until the sugar has dissolved.
Continue to simmer for three to four minutes until the mixture thickens to a syrup.
When the cake is done, remove it from the oven. Use a fork to pierce a few holes in the top.
Drizzle the orange syrup over the cake, and let it soak in for about an hour.
Serve with yogurt or whipped cream.