Prep the shrimp and sausage: Pat the shrimp dry and season lightly with a pinch of salt and pepper. Slice the sausage.
Have your chopped onion, bell pepper, celery, and garlic ready to go.
Brown the sausage: Heat the oil in a large, heavy pot or Dutch oven over medium-high. Add the sausage and cook, stirring occasionally, until browned around the edges, 4–5 minutes. Use a slotted spoon to transfer to a plate, leaving the fat in the pot.
Soften the trinity: Add the onion, bell pepper, and celery to the pot.
Cook until soft and slightly golden, 5–7 minutes, scraping up browned bits. Stir in the garlic and cook 30 seconds, until fragrant.
Toast the spices and rice: Add the Cajun seasoning, smoked paprika, cayenne (if using), salt, and black pepper. Stir 30 seconds.
Add the rice and stir to coat, toasting it gently for 1–2 minutes.
Add liquids and tomatoes: Stir in the diced tomatoes with their juices and the chicken broth. Add the bay leaf. Return the sausage to the pot and stir well.
Simmer and steam: Bring to a gentle boil, then reduce heat to low.
Cover and cook for 18–20 minutes, or until the rice is just tender and most liquid is absorbed. Avoid lifting the lid too often.
Add the shrimp: Remove the lid, quickly scatter the shrimp over the top, and gently nestle them into the rice. Cover again and cook 4–6 minutes on low, until the shrimp are pink and opaque.
Rest and finish: Turn off the heat.
Let the pot sit, covered, for 5 minutes to finish steaming. Remove the bay leaf. Fluff gently with a fork.
Taste and adjust seasoning with more salt or a squeeze of lemon.
Garnish and serve: Sprinkle with parsley and green onions. Serve hot with extra lemon wedges if you like a bright finish.