Bring a large pot (at least 6 quarts) of water to a rolling boil. Add 1 tablespoon salt. Add 12 oz linguine and cook according to package instructions until just al dente (usually 8–10 minutes). Reserve 1 cup of the pasta cooking water, then drain the pasta and toss with 1 teaspoon olive oil to prevent sticking. Keep warm.

Seafood

Prepare seafood

Pat shrimp, scallops, and calamari dry with paper towels. If using clams or mussels, scrub and debeard them; discard any that are cracked or don’t close when tapped. Season the shrimp and scallops lightly with 1/4 teaspoon salt and a pinch of pepper.

Sear shellfish

Heat a large wide skillet or sauté pan over medium-high heat. Add 1 tablespoon olive oil. When shimmering, add scallops (if large, sear 2 minutes per side) and cook until golden on each side; remove to a plate. Quickly sauté shrimp 1–2 minutes per side until just pink; remove. Briefly sear calamari 30–60 seconds until opaque; remove. (You want the seafood slightly underdone because it will finish cooking in the sauce.)

Sauce

Sweat aromatics

In the same pan over medium heat, add 2 tablespoons extra-virgin olive oil and 2 tablespoons butter. Add the chopped shallot and cook 2–3 minutes until softened. Add 4 cloves minced garlic and 1 teaspoon red pepper flakes; cook 30–45 seconds until fragrant but not browned.

Deglaze

Stir in 1 teaspoon tomato paste (if using) and cook 30 seconds. Pour in 1 cup dry white wine to deglaze, scraping browned bits from the pan. Bring to a gentle simmer and reduce by about half (3–5 minutes).

Build sauce

Add 1 cup low-sodium chicken or seafood stock and simmer 2–3 minutes. If using, stir in 1/4 cup heavy cream and bring just to a gentle simmer to thicken slightly (1–2 minutes). Add the zest and juice of 1 lemon, 1 teaspoon salt, and 1 teaspoon freshly ground black pepper. Taste and adjust seasoning.

Finish with seafood

Return the seared scallops, shrimp, and calamari to the pan along with any juices on the plate. If using clams or mussels, add them now, cover the pan, and cook 3–4 minutes until shells open (discard any that remain closed). Toss gently to coat and finish cooking for 1–2 minutes so seafood is cooked through but not overdone.

Combine with pasta

Add the drained linguine to the pan with the sauce and seafood. Toss to combine, adding reserved pasta water a few tablespoons at a time as needed to loosen and bind the sauce (use up to 1/2 cup). If desired, stir in 1 tablespoon butter and 1 teaspoon olive oil to add sheen.

Garnish and serve

Stir in 1/4 cup chopped fresh parsley and adjust seasoning with more salt, pepper, or lemon juice to taste. Serve immediately, portioned over plates, and offer extra lemon wedges at the table.