Place the orange - with skin on - ina deep saucepan and cover with cold water. Stir in the caster sugar. Slowly bring to a simmer. Cover and cook for 1 and a 1/2 hours, turning occasionally. Remove from the syrup and cool until able to handle. Cut into quarters and discard pips.
Meanwhile, bring a large frying pan of water to a simmer. Add the vinegar. Carefully break in 3 eggs. Poach until just cooked. Cool a little.
Preheat the oven to 160C. Lightly butter a 12-hole muffin pan, preferably one with straight sides.
Place the ground almonds, sugar and baking powder into a food processor. Add the orange quarters, 5 whole eggs and 3 poached eggs. Blend until smooth.
Pour the mixture into the muffin holes almost to the top.
Bake for 40 minutes, until a skewer inserted in the centre comes out clean. Turn out onto a wire rack to cool.
Great served topped with a little mascarpone or whipped cream and sprinkled with finely grated orange rind. - Makes 12 little cakes.
