Bring a medium pot of lightly salted water to a boil. Preheat oven to 350 degrees F. Spray a 9 x 13″ baking dish with cooking spray.
Break spaghetti noodles into thirds and cook according to package directions. Drain and set aside.
Meanwhile, heat a large skillet over medium high heat and spray with cooking spray. Add chicken and cauliflower to hot skillet, and sprinkle with garlic powder. Stir fry until chicken is cooked through.
Add tomatoes, sour cream, and cheese soup to chicken mixture, and stir to combine. Add cooked noodles, and stir to coat. Transfer this cheesy goodness to the prepared baking dish, and sprinkle cheese over the top.
Bake in preheated oven for 10-15 minutes until cheese is melted. (You could actually skip this step if you wanted and just melt the cheese over the pasta in the skillet before serving.)