In this case with jambalaya, tomatoes were hard to come by in the bayou, so Cajun style gumbo often omits that ingredient.
Preheat oven to 350 degrees. In a Dutch oven or skillet, melt the butter and saute the vegetables, sausage and garlic. Add the chicken and shrimp, stirring until cooked. Add the water, seasonings and tomato powder. Bring to a simmer. Add the rice and cook, uncovered, in the oven until the rice is tender, about 20 minutes.