Start with zesting the oranges and the lemon and set that aside covered for later
Juice one orange and the lemon and set aside for later
Place the two remaining oranges in a medium sized saucepan, cover them with water and bring to a boil. Let them zimmer for an hour.
Remove the oranges from the saucepan and leave to cool
Preheat the oven to 165C fan
Line a 24cm loose bottom spring tin with greaseproof paper
When cold, peel the oranges and cut them in pieces making sure there are no pips
Using a stick blender or a food processor reduce them to a pulp
Add eggs and the reserved zest to the oranges and mix until smooth
Separately mix ground almonds, baking powder and 250g of the caster sugar
Add the orange and egg mix to the dry ingredients and mix well with a wooden spoon
Transfer the mixture into your prepared tin.
Add the flaked almond around the edge of the tin or in any pattern you prefer
Cook for about 30-35 mins until golden brown and well risen
At the end of the bake is when it's time make the syrup
Add the remaining 75g caster sugar along with the remaining juice you set aside earlier to a small saucepan
Bring this to the boil while stirring. Once boiling turn it down to a zimmer for 5 mins which will thicken it and make it into a syrup
With the cake out of the tin, brush the top with the hot syrup and you'll end up a shiny golden surface