Heat olive oil in large pot. Add chopped onion and sauté for a few mins til soft. Add ground beef and cook thoroughly. Add pureed tomatoes, beans, soup and rotel. Stir everything together. Stir in chili powder and cumin. Simmer for at least 30 mins. Chili will be ready in 30 mins, but can be simmered for as long as you like. The longer it is simmered the thicker it will be. I serve this over rice, or with tortilla chips, or on its own with crusty bread.