Bring 2 tablespoons water and 1 ½ teaspoons Old Bay seasoning to a simmer over medium-low heat in a small skillet or saucepan. Reduce the heat to low. Whisk in 1 stick cold unsalted butter a tablespoon at a time, whisking until each piece is almost melted before adding the next. Do not let the butter boil, or it will separate.
Whisk in 1 tablespoon lemon juice. Serve warm.
