In a large skillet over medium heat, add a splash of oil and toss in diced onions and green bell peppers. Sauté for 7-8 minutes until they're soft and slightly caramelized, then add minced garlic. Cook for an additional 1-2 minutes until fragrant.

Crumble the ground chicken into the skillet with the sautéed vegetables. Cook for 5-7 minutes, stirring occasionally, until the chicken is browned and fully cooked through.

Sprinkle in the Cajun spice blend, stirring well to coat the chicken and vegetables evenly. Let it cook together for about 2 minutes.

In a separate bowl, mix together the tomato sauce, ketchup, Worcestershire sauce, and brown sugar until smooth. Pour this sauce over the chicken mixture in the skillet and stir to combine.

While your sauce is simmering, preheat your oven to 400°F (200°C). Split the hamburger buns and toast them in the oven for 4-5 minutes.

Once the filling is ready and the buns are toasted, spoon the Cajun chicken mixture onto each bun and sprinkle shredded cheese on top. Serve immediately.