Heat the oven to 400°F and grease a 9-by-13-inch baking dish.
Pat the shrimp dry and toss them with the Cajun seasoning and salt.
Combine the rice, tomatoes, corn, bell pepper, half the scallions, melted butter and 1/2 cup Monterey Jack in the dish.
Fold the seasoned shrimp into the rice and spread the mixture in an even layer.
Top with the remaining cheese and bake uncovered for 18 to 22 minutes, until the shrimp are opaque, curled into loose C shapes and reach 145°F.
Rest for 5 minutes and add the remaining scallions before serving.