Spaghetti with Lobster Fra Diavolo

• 2 tablespoons extra-virgin olive oil

• 1/2 medium onion, finely chopped Yellow Onions

• 4 garlic cloves, crushed

• 1/2 teaspoon red-pepper flakes

• 2 cans (28 ounces each) whole peeled tomatoes with juice, preferably San Marzano, pureed

• 2 cups water

• Coarse salt and freshly ground pepper

• 4 cups lobster stock or fish stock

• 3 lobster tails in shells

• 1 pound spaghetti

• 2 tablespoons chopped fresh basil