Preheat your oven to 175ºC (155ºC fan-forced). Prepare a loaf tin with baking paper.
In the bowl of a stand mixer, add sugar, lemon zest and thyme and rub between your fingers to infuse.
Add butter and beat for a few minutes until creamy. Whisk in the eggs.
Add milk, lemon juice and vanilla extract and whisk to combine. Your batter will likely split - don't worry! It'll come together again soon.
In a separate bowl, sift together flour, baking powder and salt. Pour dry ingredients into the wet and gently fold together until there are no dry spots remaining.
Pour batter into your prepared loaf tin and bake for 45-55 minutes until browned on top. Insert a skewer to test - when it comes out clean your loaf is ready. Remove from the oven and cool in the tin for five minutes, before transferring to a wire rack. Allow the loaf to cool completely before glazing.
To make the glaze, stir together icing sugar and lemon juice. Pour over cooled loaf. Sprinkle with sprigs of fresh thyme to garnish.