Heat oven to 200C/180C fan/gas 6 and lightly grease a 12-hole muffin tin. Mix together the flour, caster sugar, baking powder and poppy seeds in a large mixing bowl. In another bowl, whisk together the oil, milk, egg, and zest and juice from 1 of the oranges.
Working very quickly, pour the wet ingredients into the dry and barely mix together with a fork – the mixture should be lumpy, so don’t overwork it. Spoon the mixture into the tins and bake for 10-12 mins until risen and browned.
While the muffins are baking, mix the remaining zest with the granulated sugar in a small bowl. Have the remaining blood orange juice ready too.
Leave the muffins to cool for 2 mins, then transfer to a wire rack. Again working quickly, pour the juices into the sugar mix and spoon some over each muffin, repeating until it
is all used up. Leave to set for 5 mins before eating.