Heat 3 tbs olive oil in a large heavy pot or Dutch oven over medium heat until shimmering. Add the chopped onion and a pinch of salt and cook, stirring occasionally, until translucent, about 6–8 minutes. Add sliced garlic, sliced fennel, and red chili flakes; cook until fragrant and the fennel begins to soften, about 3–4 minutes.

Deglaze and build flavor

Raise heat to medium-high and add the white wine. Scrape any browned bits from the bottom of the pot. Let the wine reduce by about half, 2–3 minutes. Stir in the tomato paste and cook 1 minute to deepen the flavor.

Add liquids and simmer

Add the crushed tomatoes, fish stock, bay leaf, salt, pepper, and optional sugar. Bring to a gentle simmer, reduce heat to medium-low, and simmer uncovered for 15 minutes to meld flavors. Taste the broth and adjust seasoning (salt, pepper, or a pinch more sugar) as needed.

Seafood

Prepare seafood

While the broth simmers, pat the fish, shrimp, scallops, and calamari dry with paper towels. Season pieces lightly with a pinch of salt and pepper.

Sear firm fish (optional)

In a separate skillet, heat 1 tbs olive oil over medium-high heat. Quickly sear the white-fish pieces for 30–60 seconds per side just to develop slight color (this step is optional but adds texture). Transfer to a plate.

Add shellfish to broth

Bring the broth back to a gentle simmer. Add the mussels and clams first, nestling them into the broth. Cover the pot and cook 3–5 minutes until most shells begin to open.

Finish cooking delicate seafood

Uncover, add the seared fish pieces, shrimp, scallops, and calamari. Spoon hot broth over them once, cover, and simmer 3–5 minutes more until shrimp are pink and opaque, scallops are firm, calamari is tender, and remaining shells have opened. Discard any mussels or clams that do not open.

Adjust seasoning

Taste the stew and adjust seasoning with more salt or pepper if necessary. If the broth tastes too acidic, stir in a little more sugar (up to 1/2 tsp total).

Finishing & garnish

Brighten and serve

Remove bay leaf. Stir in the chopped parsley, fennel fronds, and lemon juice. Ladle the Sicilian seafood stew into warm bowls, making sure each bowl gets a mix of mussels/clams and other seafood. Serve immediately with lemon wedges and crusty bread for soaking up the broth.

Leftovers & notes: Refrigerate leftover stew in an airtight container up to 2 days. Reheat gently on the stovetop—do not overcook to avoid rubbery seafood. For a spicier stew, add more red chili flakes or a chopped fresh red chile when cooking the aromatics.