Creamy, no-split lemon butter sauce can be achieved with two ingredients, vigorous whisking, and your undivided attention.
Bad lemon butter sauce happens when butter splits from the lemon juice. When you see those white curds floating on top, you've done it the wrong way.
When done well, lemon butter sauce should appear creamy, with a velvety body and a bright, opaque color. You don't need to use thickeners.
To help the butter and lemon juice mix, make sure to use a low temperature. Start with heating lemon juice, but maintain a low simmer—high heat will split them apart. Add the cold butter into the juice piece by piece. Once melted, whisk the sauce vigorously to create a stable, smooth, and creamy mixture. Serve this rich and bright sauce with fish or vegetables.
Add lemon juice to a small saucepan and bring to a slow, gentle simmer.
Add a cube or two of cold butter to the pan and whisk rapidly, slowly melting the butter in the process. Repeat, whisking vigorously after each addition, until all of the butter has been used. Season with a pinch of salt, give it one last whisk, and serve.
You can add about 1-2 tbsp of mayonnaise to the sauce.
