Heat the butter, olive oil and garlic in a large skillet over medium-high heat until fragrant, about 1 minute. Add the Cajun seasoning and shrimp and cook, stirring, until the shrimp begin to curl, about 1 minute. Season with salt and pepper.
Add the tomatoes and scallions to the skillet and cook, stirring, about 1 minute. Add the rice and 1/4 cup water and continue to cook until the rice is warmed through and the shrimp are opaque, about 3 more minutes. Stir in the parsley and serve with lemon, if desired.
Per serving: Calories 357; Fat 11 g (Saturated 3 g); Cholesterol 176 mg; Sodium 537 mg; Carbohydrate 40 g; Fiber 3 g; Protein 23 g