Step 1Rinse the mussels well and beard if necessary. Set them aside.
Step 2Heat the oil and butter in a large skillet over medium-high heat. Add the shallots and garlic and cook, stirring, until they're fragrant, about 2 minutes.
Step 3Add the tomatoes and break them up a bit with a wooden spoon. Cook, stirring frequently until the tomatoes have softened, about 5 minutes.
Step 4While the tomatoes cook, bring plenty of salted water to a boil in a large saucepan. Add the linguine and cook 3 minutes, until al dente.
Step 5Add the mussels to the skillet, cover and cook until the mussels have opened up completely, about 3 minutes. Remove them from the skillet and keep them warm.
Step 6Drain the linguine and add it to the skillet. Add the lemon juice and the parsley and toss well. Divide the pasta among 4 bowls and top it with the mussels.