Ingredients
2 cups sugar
2 tablespoons plus 1 1/2 teaspoons cornstarch
Large pinch of salt
2 1/2 cups hot water
7 tablespoons unsalted butter
1/2 cup freshly squeezed lemon juice
2 tablespoons freshly grated lemon zest
Preparation
In a heatproof bowl set over (but not touching) simmering water, mix together sugar, cornstarch, and salt. Add hot water and cook, 3 to 5 minutes, whisking gently, until thick.
Add the butter, lemon juice, and zest and continue cooking, stirring gently, for about 5 minutes. Cool slightly before using, but do not refrigerate (the sauce will become aspic-like) and do not reheat.
