Boil spaghetti in salted water until al dente, then drain.

Sauté garlic and onion in olive oil until fragrant.

Add shrimp and mussels, cook until they start to color.

Pour in white wine, let it simmer for 2 minutes.

Add diced tomato, salt, and pepper. Cook until tomatoes soften.

Toss in cooked spaghetti and mix well with the sauce.

Serve hot, topped with parsley if desired.