Place a whole orange (skin on) in a saucepan and cover with water. Bring to the boil, cover with a lid, and turn to simmer for 40 minutes. Drain orange, reserving 125ml of the cooking liquid.
Once the orange has cooled, cut into chunks then blend into a puree with either a hand blender or food processor. Keep aside.
Preheat oven to 180°C. Grease a 20cm square cake tin.
Whip sugar and eggs until very light and fluffy. Gently fold in almond meal, baking powder, and orange puree until well combined.
Pour batter into the cake tin and bake in the oven for 50 - 60 minutes. Test cake by skewering the center with a clean metal skewer. If it comes out clean and dry then the cake is cooked.
For the syrup: Combine the orange liquid and honey in a small saucepan. Bring to boil then turn to simmer and cook down until reduced by half and thickened.
Combine orange honey syrup with toasted almonds and spread evenly over the cake.
Serve with a dollop of cold mascarpone cream or vegan yoghurt.