Scrub and clean the mussels and remove the beards on the mussels by pulling them off. Drain and set aside.
Heat up a skillet on medium heat. Add the olive oil. Saute the garlic a few times before adding the mussels. Stir and toss the mussels. Add the white wine and diced tomato. Cover the skillet with its lid and steam for 1 minute or until all mussels are open.
Add the lemon juice, salt (to taste) and parsley. Stir to combine well. Serve hot.
Notes
I served the mussels with plain spaghetti. Just ladle the sauce and the mussels over for a complete meal.