Place everything but the oil and lemon juice in the blender or processor container.
Process 5 seconds in the blender; 15 seconds in the processor.
With the motor running, add the oil, first in a drizzle, then in a thin, steady stream.
When all the oil has been added, stop the motor and taste.
Add lemon juice to your taste. If the sauce is too thick, thin with hot water or lemon juice.
If too thin, process a little longer.