Preheat oven to 170 degrees celsius (fan-forced). Grease a large 13 X 32 cm loaf tin and set aside (see notes).
Place the caster sugar, eggs, vegetable oil and lemon zest into the Thermomix bowl, insert the butterfly and mix on Speed 4, 10 seconds. Scrape down the sides of the bowl and repeat. Remove the butterfly.
Add the salt, greek yoghurt and self-raising flour and mix on Speed 4, 10 seconds. Scrape down the sides of the bowl and repeat for a further 5 seconds or until combined.
Pour into the prepared loaf tin and bake for 40 minutes or until cooked through (see notes).
Allow to cool in the tin for 10 minutes before transferrring to a wire rack to cool completely.
To make the lemon icing glaze, place the softened butter, icing sugar, lemon juice, lemon zest and salt into a clean Thermomix bowl and mix on Speed 7 until smooth and creamy (scraping down the sides of the bowl occasionally).
Pour the glaze over the cooled loaf and allow it to drip down the sides.
Grate over extra lemon zest (optional).