How to Make It
Bring the wine to a boil in a medium saucepan. Add the mussels, cover and cook over high heat until they open, about 2 minutes. Using tongs, transfer the mussels to a bowl. Add the clams to the saucepan, cover and cook until they start to open. Transfer them to the bowl with the mussels. Pour the cooking liquid into a small glass measure, leaving behind any grit. Shell the mussels and clams and return them to the bowl.
Heat the olive oil in a medium saucepan. Add the garlic and cook over low heat until golden, about 3 minutes. Add the red pepper and half of the cherry tomatoes and cook over moderate heat, crushing the tomatoes with a wooden spoon, until the juices thicken, about 4 minutes. Add the reserved shellfish cooking liquid and simmer over moderate heat until slightly reduced, about 3 minutes.
Cook the spaghetti in a large pot of boiling salted water, stirring occasionally, until al dente. Meanwhile, bring the sauce to a simmer over moderate heat. Add the shrimp and cook for 1 minute. Add the remaining cherry tomatoes and the reserved mussels and clams and simmer briefly to heat through.
Drain the spaghetti and return it to the pot. Add the seafood sauce and toss to coat. Season with salt and black pepper and transfer to a warmed bowl. Sprinkle with the parsley and serve at once.