Put the oranges and walnuts in a blender or food processor and whiz until smooth.
Add the milk and flax-seeds, then rest for 10 minutes.
Meanwhile, mix the flour, baking powder, sugar and salt in a mixing bowl.
Preheat the oven to 180°C.
Add the oil and vanilla to the orange blend.
Pour this mixture over the flour mixture and combine gently. Don’t overmix.
Transfer the batter into two or three small silicon cake tins or 4 mini loaf tins or one larger tin.
Bake for about 25 minutes, until golden and an inserted toothpick comes out clean. For the large version, the baking should take about 35 minutes.
Rest the cakes in the tin for 5 minutes, then turn them onto a wire-rack to cool.
When completely cooled, finish with icing, plant-based buttercream or just dust with icing sugar.