Add the ground beef and onion to a large pot or Dutch oven. Cook over medium heat for about 7 minutes, stirring and breaking up the meat, until the beef is browned.
Drain off the excess fat and return the beef mixture to the pot. Add the chili powder and stir for 30 seconds.
Add the beans and diced tomatoes. I usually add ¼ cup (60ml) at this point too. Bring the chili to a gentle boil. Cover, reduce the heat to low and simmer for 20 minutes.
Remove the lid and simmer for 5 minutes more, stirring occasionally. Serve with sour cream, shredded Cheddar or chopped cilantro (coriander), if liked.
