Spaghetti with Dungeness Crab

The meat from two cooked Dungeness crab (I buy them fresh cooked from the fish market and crack them at home)
Lots of minced shallots (about 1/2 – 3/4 of a cup)
4 tablespoons unsalted butter divided
Zest of two lemons
Red chili flakes to taste
Chopped parsley
1 pound spaghetti

This sauce is made while the pasta is boiling.
Boil the spaghetti in highly salted water for one minute less than package instructions.  While the pasta is cooking, melt two tablespoons of butter in a saute pan large enough to hold the pasta.  Add the shallots, lemon zest and red chili flakes and cook over medium heat until the shallots are soft.  Before draining the pasta, scoop out one cup of the pasta water.  Add 1/2 cup of the pasta water to the pan with the shallots and bring to a boil.  Add the pasta and remaining two tablespoons of butter to the pan and toss, adding more pasta water if it gets too dry.  After about a minute the pasta should be al dente.  Add the cooked crab meat and fold into the pasta, careful not to break up the lumps of meat too much.  Turn off the heat.  (You don’t want to cook the crab meat, just heat it a bit).  Sprinkle with parsley and serve.