In a small bowl, mix the cumin, paprika, garlic powder, salt, and pepper. Rub the spice mixture over the chicken breasts.
In a large skillet, heat the olive oil over medium-high heat. Add the chicken breasts and cook for 5-6 minutes on each side or until golden brown and cooked through. Remove the chicken from the skillet and set aside.
In the same skillet, add the chopped onion and sliced bell peppers. Cook for 5 minutes, or until the vegetables are softened.
Add the minced garlic to the skillet and cook for an additional 1 minute.
Pour in the chicken broth and diced tomatoes, then stir in the dried oregano and ground coriander. Bring the mixture to a simmer.
Return the cooked chicken breasts to the skillet and simmer for an additional 5 minutes, allowing the flavours to meld together.
To serve, place a chicken breast on each sandwich roll or slice of French bread. Spoon the vegetable and sauce mixture over the chicken. Top with sliced avocado and chopped cilantro.