Heat the vegetable oil in a large pot over medium heat. Add the ground beef and cook, breaking it apart with a spoon, until it is no longer pink.
Add the diced onion, bell peppers, and minced garlic to the pot. Stir and cook for 4 to 5 minutes until the vegetables begin to soften.
Sprinkle in the Cajun seasoning and cayenne pepper. Stir for 30 seconds to coat the meat and vegetables evenly.
Pour in the diced tomatoes with their juice and the beef broth. Bring the mixture to a boil, then reduce the heat and simmer uncovered for 15 minutes.
Taste and add salt if needed. Remove from heat and let the stew rest for a minute before serving.