Line the base and grease the sides of a large loaf tin and preheat your oven to 180 degrees celsius (fan forced)
Carefully cut the skin off one orange and place into Thermomix bowl. Mix for 45 seconds speed 10. Scrape down the sides and mix for a further 30 seconds, speed 9 or until finely grated.
Add the softened butter and caster sugar and mix for 30 seconds on speed 3 or until pale and creamy.
Add the remainder of your cake ingredients and mix for 10 seconds on speed 4 or until your mixture is smooth and well combined. Mix for a further 5 - 10 seconds on speed 4 if necessary.
Pour the mixture into your prepared cake tin and place in the oven to bake for 30 - 35 minutes or until the cake is cooked through when tested with a skewer.
Carefully remove the cake from the oven and let it cool in the tin for 15 minutes before transferring to a wire rack to cool completely.
Icing
Add the icing ingredients to a clean and dry Thermomix bowl and mix for 30 seconds, speed 4 or until smooth and icing is a spreadable consistency. See notes.
Use a spatula or a butter knife to then spread the icing over the cake.
Notes
You can choose to grate the orange rind using a hand grater if you prefer.It is important to use softened butter for this recipe. If the butter is too firm, the time it takes to combine with the orange rind and caster sugar will be longer.Either fresh or store bought orange juice can be used for the cake and icing.Store in an airtight container at room temperature and consume within five days.To freeze, place into a freezer safe container and store for up to two months.This Orange Butter Cake can be frozen either plain or iced.When making the icing, you are aiming for a spreadable consistency. You may need to add an extra 1 tablespoon of water.