Bring a large pot of water to a full rolling boil and add salt generously — the water should taste clearly seasoned. Add the linguine and cook according to the package directions until al dente — approximately 9–10 minutes. Unlike the Roman pasta dishes in this collection where the pasta finishes cooking in the sauce, the linguine here is cooked to full al dente before adding to the cream sauce — cream-based sauces do not absorb into pasta the way starchy pasta water-based emulsions do, and finishing in a cream sauce does not add meaningful flavour penetration. Before draining, reserve 120ml of the starchy pasta water in a heatproof jug — it will be used to loosen the sauce if it thickens beyond the correct coating consistency. Drain and set aside.

Pat the shrimp completely dry on both sides with paper towels — thorough drying is the most critical preparation step for a proper sear. Any surface moisture converts to steam the moment the shrimp contacts the hot oil, dropping the pan temperature and producing pale, steamed shrimp rather than the golden-crusted, Maillard-caramelised surface that this dish requires. In a bowl, toss the dried shrimp with the 9g of Cajun seasoning until every surface is evenly coated. Allow to sit for 5 minutes — this brief marinating period gives the spice's oil-soluble aromatic compounds time to begin penetrating the shrimp's surface layer, producing a more integrated flavour rather than seasoning that simply sits on the outside. Heat the 45ml of olive oil in a large, deep skillet over medium-high heat until shimmering. Add the seasoned shrimp in a single layer — work in batches if needed to maintain space between each piece, as crowding drops the temperature and produces steaming rather than searing. Sear undisturbed for 2 minutes — the Cajun seasoning's paprika and spices caramelise against the hot pan surface, creating a deeply coloured, aromatic crust with more flavour complexity than unseasoned shrimp would develop in the same time. Flip and cook for 1–2 minutes more until just cooked through and opaque throughout. Transfer to a plate immediately — the shrimp are pulled slightly before being fully done because they return to the pan at the end and will finish in the warm sauce.

Without cleaning the pan — the Cajun-seasoned fond from the shrimp sear is concentrated flavour — reduce the heat to medium and add the 30g of butter. As the butter melts and foams, add the minced garlic and cook for 45 seconds, stirring continuously, until fragrant and very lightly golden. At medium heat with the pan's residual warmth from the shrimp searing, garlic moves quickly toward browning — 45 seconds of continuous stirring is the window between fragrant and bitter. Add both the red and yellow bell pepper slices to the pan. Cook for 4–5 minutes, stirring occasionally but not continuously — allowing the slices to sit against the pan surface for 60–90 second intervals produces the slight char at the edges that gives the peppers their flavour character alongside their tender-crisp texture. The colour combination of red and yellow is not purely aesthetic — each bell pepper variety has a slightly different sugar content and flavour profile, and together they produce a more complex, more interesting pepper presence than a single colour alone. Add the second tablespoon of Cajun seasoning, the smoked paprika, and the cayenne pepper directly to the peppers. Stir constantly for 30 seconds — the dry spices toast against the hot pan surface in the residual fat, blooming their aromatic compounds and deepening their flavour character. Toasted spices produce a more complex, rounded result than spices added directly to liquid, which simply hydrate rather than develop through heat contact.

Add the cooked al dente linguine to the cream sauce in the skillet. Toss with tongs for 1–2 minutes, turning the pasta through the sauce continuously and ensuring every strand is completely coated. Unlike the emulsion-based Roman pastas where tossing is the mechanical emulsification step, here the tossing purpose is sauce penetration and coating — ensuring every strand is uniformly covered and that the pasta's starch releases slightly into the cream sauce, thickening and enriching it further. The pasta will absorb some of the sauce during this tossing period and the overall volume will reduce slightly — this is correct and expected.

Return the seared shrimp to the pan along with any accumulated resting juices from the plate — these juices contain Cajun-seasoned rendered shrimp fat and represent concentrated flavour that should always go back into the sauce rather than being discarded. Add the 15ml of fresh lemon juice and half of the chopped parsley. Toss gently for approximately 1 minute — gentle tossing rather than the vigorous motion used during pasta combining prevents the shrimp from breaking apart and ensures they warm through without continuing to cook. The lemon juice provides the acid brightness that cuts through the cream sauce's richness and makes the Cajun spicing taste more vivid rather than buried in dairy fat. Taste and adjust — the dish needs to be assessed for salt, heat level, and acidity simultaneously. Add black pepper generously; add more Cajun seasoning or a few drops of hot sauce if additional heat is wanted; add more lemon if the cream feels heavy.

Divide among four warm plates or shallow bowls, using tongs to ensure each portion receives an even distribution of linguine, shrimp, and bell pepper pieces. Spoon any remaining sauce from the pan over each portion. Scatter the remaining chopped parsley over each bowl — the fresh, green herb contrast against the deep orange-red Cajun cream sauce is both visual and flavour completion. Serve immediately.