Fill a blender with hot water; set aside. 

Melt butter in a small saucepan over medium heat until foaming. Remove pan from heat.

 Drain blender and dry well. Put egg yolks and 2 tablespoons lemon juice in blender; cover and blend to combine. 

Working quickly and with blender running, remove lid insert and slowly pour hot butter into blender in a thin stream of droplets, discarding the milk solids in bottom of the saucepan. Blend until creamy sauce forms. 

Season to taste with salt and pepper, and with more lemon juice. Serve immediately.