See NOTE below about the yield of the sauce. This recipes makes about 1 gallon of crab gravy. Reduce the portions as desired, but you will be very happy that you have leftovers in the freezer. Trust me!
Make the crab gravy: In a large, heavy-bottomed saucepan or Dutch oven, heat the olive oil, onions, garlic, anchovies and crushed red pepper together over medium-low heat and cook until the onions and garlic are soft and starting to brown. At this point, the anchovies will have fully dissolved into the oil.
Add half the basil and sauté for about two minutes, to release its flavor, while stirring.
Add the tomatoes, water, salt and black pepper and bring mixture to a light boil, then immediately reduce the heat to a low simmer and submerge all of the crabs in the tomatoes.
Partially cover the pot and simmer for about 2½ hours, stirring regularly. Remove the crabs from the sauce at this point and hold them warm, covered, in a 200°F oven, while preparing the pasta. (See NOTE below about the amount of sauce that this recipe yields). Taste and adjust seasoning of the sauce, if necessary, and fold in the remaining basil.
Heat a large pot of water to boiling to cook the pasta. In the meantime, place about three cups or so of the crab gravy in a large skillet over low heat.
Cook pasta in a large pot of salted boiling water until two minutes less than al dente. At this point, transfer the pasta and about ½ cup pasta water to the skillet with the sauce. Finish cooking the pasta in the delicious sauce so that it will soak up all of those delicious flavors! Add more pasta water and sauce as desired or needed.
Transfer the pasta to a serving bowl and enjoy! Serve the crabs on the side or after enjoying the pasta. Buon Appetito!