Combine sugar, cornstarch (cornflour) and lemon zest in a small saucepan.
½ cup (100g) white granulated sugar, 3 Tablespoons (20g) cornstarch, 1 Tablespoon lemon zest
Add yellow food coloring or tumeric (just for color-this is optional)
Pinch of turmeric or powdered yellow food coloring
Pour in the milk and lemon juice.
1 cup (250ml) milk, ½ cup (125ml) freshly squeezed lemon juice
Turn the stove on to medium low heat. Whisk constantly until the mixture starts to bubble and thicken.
Within 6 to 8 minutes, the mixture should thicken sufficiently, and you'll know it's ready when it coats the back of a spoon.
Remove the pot from the heat and stir in the butter until it has melted.
2 Tablespoons (30g) salted butter, at room temperature
Allow it to cool for a few minutes before transferring it to the fridge, where the lemon curd will thicken further into a soft spreadable texture.