Heat olive oil in a large skillet over medium heat. Add the chopped onion and bell pepper, sautéing for about 5 minutes until softened.

Stir in the minced garlic and cook for an additional minute until fragrant.

Add the ground chicken to the skillet, breaking it apart with a spatula. Cook until browned and cooked through, about 6-8 minutes.

Sprinkle in the Cajun seasoning, smoked paprika, salt, and black pepper. Stir to combine.

Pour in the chicken broth, Worcestershire sauce, and tomato paste. Bring the mixture to a simmer and let it cook for about 10 minutes, stirring occasionally, until the sauce thickens slightly.

While the mixture simmers, toast the hamburger buns if desired.

To serve, spoon the Cajun chicken mixture onto the bottom half of each bun. Top with shredded lettuce, diced tomatoes, and shredded cheddar cheese. Place the top half of the bun on each sandwich.