For the tomato sauce: Heat a heavy skillet over medium heat. Add the olive oil and diced onions and cook until the onions become transparent. Stir in the basil, tomatoes and some salt and black pepper and simmer for 15 minutes.
For the cioppino: Heat the olive oil in a large pot and saute the onions until transparent. Add the garlic and saute until it begins to brown. If available, stir in crab butter and let cook slowly for 5 minutes (crab butter is saffron yellow in color and adds a distinctive rich flavor). Pour in the wine to keep the butter and garlic from burning. Add the tomato sauce, tomatoes and red pepper flakes and simmer for about 15 minutes.
Add the broth, crabs with their liquid and roe and some salt and black pepper. Cover and continue to simmer over low heat for about 8 minutes. Add the clams, mussels and prawns and cook for 2 more minutes. Serve in a bowl and sprinkle with fresh parsley.
If your crab is cooked ahead of time, add it to the recipe at the same time you add the clams, prawns and mussels.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.