Cut all peel and white pith from lemons; discard.
Working over a medium bowl, cut lemons along sides
of membranes to release segments into bowl.
Squeeze in juice from membranes and discard
Mix in anchovies, oil, and red pepper flakes,
breaking up lemon segments against the side of the
bowl with a spoon; season with salt and pepper.
DO AHEAD- Dressing can be made 4 days ahead.
Transfer to a jar; cover and chill.