Place softened butter and caster sugar in a mixing bowl and mix together until light and creamy. (You can use an electric beater, or I just do by hand with a fork).
Add egg and beat mixture to combine. Add vanilla, blood orange juice and zest to the creamed butter and sugar and mix well.
Gradually add sifted self raising flour to the mixture and stir until the mixture forms a smooth dough. (Note: I use salted butter for this recipe. If you are using unsalted butter, I recommend adding a pinch of salt to the dough when adding the flour.)
Place dough in the fridge to chill for at least 20 minutes before making the cookies. This makes the dough much easier to work with and will help stop cookies from spreading too much during baking.
Remove chilled dough from the fridge. Make tablespoon sized balls of cookie dough and roll in caster sugar to coat.
Place dough balls on the lined baking trays, leaving space between each to allow for spreading.
Remove cookies from the oven and allow to cool on the trays for 5 minutes before transferring to a wire rack to cool completely.
To make the icing, combine 3 cups of icing sugar (confectioners/powdered sugar) and 2 Tablespoons of blood orange in a bowl and stir well to create a smooth icing mixture. Spread blood orange icing over the top of each cookie. Leave cookies on the rack until the icing has set completely.
Notes
Blood orange cookies will keep for up to 5 days in an air tight container.You can also freeze un-iced cookies for up to 3 months. Alternatively, freeze uncooked cookie dough (that hasn't yet been rolled into balls and coated in caster sugar) by wrapping tightly in non stick paper and then a freezer safe bag. Then when you want to bake the cookies, simply defrost the dough at room temperature for around 30 minutes before rolling into balls, coating with sugar and baking.