In a large nonstick sauce pan, over medium heat, brown ground beef with onions. Cook until the beef is no longer pink.

Add in the diced tomatoes, kidney beans, black beans, tomato sauce, water, and seasonings (chili powder, cajun seasoning, salt and pepper). Stir to combine well. 

Bring to a boil, reduce heat and simmer, covered, for at least 20 minutes. Stir occasionally to avoid sticking.