Cook the rice according to package directions. My favorite method of cooking rice is to use the rice cooker. I just put the rice and water in the rice cooker in the morning, and the cooked rice is waiting for me later in the day. See how to cook rice in a rice cooker.
Defrost frozen corn and peas in the microwave.
Heat the oil in a large non-stick frying pan over medium-high heat. Add the onion, and cook, stirring periodically, for 3 minutes. Add the sausage, and cook, stirring periodically, for 7 minutes, or until the sausage is browned.
Add garlic and Cajun seasoning, and stir for 1 minute. Add tomato puree and stir. Simmer for 3 minutes.
Add corn, peas and rice. Stir until combined. Add salt, pepper and more Cajun seasoning to taste.