Nutrition per serving may change if servings are adjusted.
1 large egg
2 large egg whites
3/4 cup sugar
1 tablespoon freshly grated lemon zest
2/3 cup lemon juice, juice
1 tablespoon butter
Whisk together egg, egg whites, sugar, lemon zest and juice in a medium nonreactive saucepan. Add butter and cook over low heat, whisking constantly, until thickened, 5 to 7 minutes. Do not let sauce come to a simmer. Transfer to a small bowl and let cool slightly; serve warm.
Make Ahead Tip: Cover and refrigerate for up to 2 days.