Bring a large pot of salted water to a boil.

Meanwhile, toss shrimp with 1 teaspoon of the Cajun seasoning and 1/4 teaspoon of the salt.

Season steaks with 1 teaspoon of the Cajun seasoning and remaining 1/4 teaspoon salt.

Heat 1 tablespoon of the oil in a large, deep skillet over high heat.

Add shrimp and cook, stirring occasionally, until just cooked through, 3 to 4 minutes.

Transfer to a large plate and return the skillet to medium-high heat.

Add garlic, celery, bell pepper and onion to the skillet, and cook, stirring occasionally until browned, about 15 minutes.

Stir in broth and remaining 2 teaspoons Cajun seasoning and simmer until slightly reduced, 2 to 3 minutes.

Remove the skillet from the heat.

Meanwhile, cook linguine in boiling water until al dente, about 10 minutes; reserve 1/2 cup pasta water.

Heat remaining 1 tablespoon oil in a medium cast-iron skillet over medium-high heat and cook steaks, flipping once until deeply browned, about 10 minutes.

Reduce heat to medium-low and cook until medium-rare (about 130F) or desired doneness, about 5 minutes more.

Allow steaks to rest 5 minutes; discard twine and slice.

Add drained pasta and cream to the skillet with vegetables and toss well.

Add shrimp, parsley, lemon juice and reserved pasta water, if needed to moisten, and toss again.

Serve sliced steak over pasta, with any juices drizzled over the top.