Clean the mussels. Saute the onion and garlic in the olive oil in a large pot. Add the lemon slices when the onion is soft.
Whirl the tomatoes and tomato paste in a food processor. Add to the pot with the basil, cayenne and black pepper and salt.
Simmer over low heat, stirring occasionally, about 25 minutes. Add the wine and simmer 15 to 20 minutes more.
Cook the linguine until al dente and drain well.
Turn out into a shallow bowl. Add the mussels to the simmering sauce and cook about 6 to 8 minutes, until the shells open.
Discard any unopened shells. Pour the sauce with mussels over the pasta and mix very gently.
Sprinkle with the chopped parsley and serve.