Preheat oven to 180°C (160°C fan, gas 4). Line a baking tray with baking paper.
Grate the zest from the oranges.
Blitz with the almonds in the blender.
Melt the butter in a pan then allow to cool.
Whisk the eggs with the sugars and salt until frothy.
In a second bowl, mix the flour, baking powder and orange-almond mix. Stir in the egg mixture and the cooled butter.
Pour or spoon into the prepared springform tin and spread level.
Bake in the oven for 50 minutes until golden brown and a skewer inserted into the centre comes out clean. Remove from the oven, cool slightly, carefully turn out onto a wire rack and leave to cool. Remove the baking paper.
Peel the oranges, cutting off all the white pith.
Cut out the blood orange segments.
Halve the sponge horizontally, spread with the bottom layer with lemon curd and place the other layer on top. Dust with icing sugar and serve with orange segments.