- ¼ cup of lemon juice
- ½ tbsp of grated lemon zest
- 1/8 cup of unsalted butter
- ¼ cup of sugar
- 1 egg
1. Combine all the ingredients in a medium saucepan.
2. Cook over medium-low heat and stir.
3. Remove from the heat when it thickens.
4. Transfer into a bowl and let it cool before using it.