Pat shrimp dry, then toss with about half the Cajun seasoning.
Heat oil in a large skillet over medium-high. Brown the sausage. Transfer to a plate.
Add onion and bell peppers to the skillet. Season with salt and black pepper. Cook until softened.
Stir in garlic, smoked paprika, and a pinch of cayenne. Cook until fragrant, about 30 seconds.
Pour in chicken broth to deglaze, scraping up browned bits. Simmer until reduced by half.
Push veggies to the sides. Sear shrimp in the center until just pink, 1 to 2 minutes per side.
Return sausage. Sprinkle remaining Cajun seasoning, add butter and lemon juice, and toss. Finish with parsley.