Preheat the oven to 350 degrees Fahrenheit.
Melt 1 tablespoon of the butter in a large pot or Dutch oven over medium-high. Add the sausage, and cook, stirring constantly, until browned, 7 to 9 minutes
Add the remaining 1 tablespoon butter to the pot. When melted add the celery, bell pepper, and onion and cook stirring often, until tender, about 6-7 minutes. Add the garlic, and cook, stirring often, for about a minute.
Reduce the heat to medium, and add the salt, pepper, thyme, oregano, paprika, and cayenne pepper; cook, stirring constantly, until aromatic, about 1 minute.
Add the rice and tomato paste, and cook, stirring constantly, until toasted, about 3 minutes.
Add the broth and the tomatoes, stirring to loosen browned bits from bottom of the pot.
Increase the heat to high and bring to a boil. Stir in the shrimp and half of the scallions. Cover and bake in the preheated oven until the rice is tender, about 30 minutes.
Remove from the oven and let stand 5 minutes. Sprinkle with the remaining scallions just before serving.