Melt 1/2 pound of butter in a saucepan over medium heat. Remove pan from heat and let stand 3 minutes. Skim foam from off the top.
Combine 3 egg yolks, 1 tablespoon lemon juice, 1 tablespoon water in blender for 2 seconds.
With blender at medium speed, add 1/2 of the melted butter in slow stream through lid. Add 1 tablespoon warm water to thin the sauce, then slowly add remaining butter. Leave the milky solids in pan.
Thin with 1-2 tablespoons water and whisk in salt and pepper.