Chop the onion and peppers so they are small pieces. Add the hamburger, onion, and peppers to a skillet. Cook over medium heat until the hamburger is browned and the vegetables are tender. Making sure to stir occasionally.
Season the meat and vegetables with the chili powder, salt, garlic powder, and pepper.
While the meat and vegetables are cooking, cut the Velveeta into cubes. They don't have to be small, but this will help it to melt faster).
Add the Velveeta to the slow cooker, along with the meat mixture. Mix together. Add the tomatoes and tomato paste and mix together. Turn the slow cooker on high and cook for about 45 minutes to an hour.
Serve with your favorite chips, crackers, or vegetables.