Cut the tops off of the peppers and remove the core & seeds. Cut out eyes and mouth to form the face of the jack-o-lantern. Place the peppers in a large saucepan and cover with water. Bring to a simmer and cook 3-4 minutes, just until the peppers are slightly softened. Drain, rinse with cold water drain on paper towels. Set aside.
Add olive oil to a large skillet set over medium-high heat. Add onions and riced cauliflower. Saute for 5-6 minutes until slightly softened.
Add ground meat, garlic powder, cumin, salt, pepper, garlic, and paprika. Mix well and cook until meat is browned. Stir in tomato paste and chicken stock. Turn off heat.
Preheat oven to 350 degrees and coat a baking dish with nonstick spray.
Place peppers in the baking dish and spoon in filling.