When using fresh tomatoes they must be peeled first. Dip them briefly in boiling water to loosen the skins. Peel, cut in half, remove and discard the seeds. Dice the tomatoes and have ready beside the stove. Bring the water to a boil in a large pot and season with salt while you prepare the sauce. The pasta will cook in 10 minutes and the sauce will take 15 minutes to cook entirely.
Drain the anchovy fillets, rinse off the excess salt under cold water, pat dry, and chop roughly. Heat the olive oil in a sauce pan over medium heat. When hot, add the chopped anchovy fillets and saute over medium heat until the anchovies actually begin to dissolve and melt away. Add the rings of sausage and saute briefly before adding the clams in their shells. Add the garlic to the pan and before the garlic begins to brown, add the diced tomato, salt and pepper and cook for 5 to 8 minutes, before adding the white wine. Place a lid on the pan and cook until the clams steam open.
When the water is boiling, cook the pasta according to package directions, timing it so the pasta will be completed at about the same time as the sauce. Just before you drain the pasta, add the basil to the sauce and continue cooking for just a minute longer. Remove the sauce from the heat and toss in a bowl with the drained pasta.