Coat an unheated large nonstick skillet with cooking spray. Preheat skillet over medium-high heat. In a medium bowl toss together chicken, garlic, and chili powder. Add to hot skillet and cook for 4 to 6 minutes or until chicken is no longer pink. Remove chicken from skillet and set aside.
Add canola oil to skillet and cook onion and sweet pepper over medium heat for about 5 minutes or until tender. Stir in spinach and fresh squeezed lime juice.
Coat a 2-quart square baking dish with cooking spray. Spread about 1/2 cup of the salsa in the baking dish and top with half of the prepared riced cauliflower, half of the chicken mixture, and half of the vegetable mixture.
Pour half of the remaining salsa over the vegetables and top with half of the cheese. Repeat layers once and add halved cherry tomatoes to top. except Do not top with the remaining cheese yet.
Bake, covered, for 20 to 25 minutes or until heated through. Sprinkle with the remaining cheese. Let stand for 5 minutes before serving. If desired, garnish with cherry tomatoes, chopped avocado, and/or a dollop of sour cream.