Heat the olive oil in a large stockpot over medium heat. Add the onions and
parsley and cook, stirring frequently, until translucent, about 5 minutes.
Add the garlic, rosemary, tomato sauce, wine, clam juice, butter, sugar and
pepper and bring to a boil. Reduce the heat and simmer, partially covered,
stirring occasionally, for 45 minutes.
Add the crab pieces and stir to coat with the sauce. Bring the sauce back to a
boil and simmer, covered, stirring occasionally, until the crab is just heated
through, about 15 minutes. Taste the sauce and add salt, if desired.
Serve with sourdough bread for soaking up the sauce.