Heat the olive oil in a large pot over medium heat. Add the ground beef and cook until browned, breaking it up with a spoon as it cooks.
Add the diced onion and bell peppers to the pot. Cook for 4 to 5 minutes until the vegetables start to soften.
Stir in the minced garlic and cook for 1 minute until fragrant.
Pour in the diced tomatoes and beef broth. Add the Cajun seasoning and a pinch of salt.
Bring the mixture to a simmer. Let it cook for 15 minutes, stirring occasionally, until the stew thickens slightly.
Taste and adjust salt if needed. Ladle into bowls and top with chopped green onions before serving.