Saute the beef and onion in a big pot or Dutch oven or large pot until the beef for 7 minutes or until the beef is browned.
Stir every few minutes with a wooden spoon to help crumble up the meat.
Drain the fat off the meat mixture and return the meat to the pan.
Add the chili powder and stir.
Add the beans, 1/4 cup of water and the diced tomatoes to the pot and bring to a slow boil.
Cover and reduce the heat to low, then simmer it for 20 minutes.
Take the lid off and simmer for 5 minutes, stirring occasionally.
Ladle the chili into bowls and serve hot.
You can top it with sour cream, cheddar cheese or chopped cilantro.
This chili will keep refrigerated for up to 5 days or you can freeze it for up to 3 months.
