In a medium bowl, toss the shrimp with Cajun seasoning until evenly coated. Set aside.
In a large skillet, heat the olive oil over medium heat. Add the diced onion and bell pepper, cooking for about 5 minutes until softened. Stir in the minced garlic and cook for an additional 1 minute.
Add the rice to the skillet, stirring to coat it with the oil and vegetables. Cook for 2-3 minutes until the rice is slightly toasted.
Pour in the chicken broth and diced tomatoes (with their juices). Stir to combine, then bring to a boil.
Reduce the heat to low, cover, and simmer for 15 minutes.
After 15 minutes, add the shrimp and frozen peas to the skillet. Stir gently, cover, and cook for an additional 5-7 minutes, or until the shrimp are pink and cooked through and the rice is tender.
Season with salt and pepper to taste. Remove from heat and let it sit for a few minutes before serving. Garnish with sliced green onions.