Preheat oven to 350 degrees F.
Spray a 13-inch x 9-inch casserole or baking dish with cooking spray. Spread diced butter around the bottom of the pan.
In a large bowl, stir together shrimp, uncooked rice, soups, tomatoes, onion, bell peppers, garlic, Cajun seasoning, salt and pepper.
Pour shrimp mixture over butter into prepared baking dish. Cover tightly with aluminum foil and bake for 30 minutes.
Stir well, cover tightly again, and bake for an additional 35-40 minutes, or until rice is fluffy and liquid has been absorbed.