Add remaining ingredients and bring to a simmer. Simmer, uncovered, for 30 minutes.
Garnish with toppings of choice.
ALTERNATIVE SLOW COOKER INSTRUCTIONS:Brown ground beef and onion in a large skillet or Dutch oven. Drain off the fat.Transfer beef and onion to a slow cooker. Add remaining ingredients, but only use 2 cups of water instead of 3. Cover and cook on LOW heat for 6-8 hours or on HIGH heat for 3-4 hours. If you want a thinner soup, you can always add extra water to the pot as the soup is cooking.Garnish with toppings of choice.Recipe Variations:
Substitute ground chicken or ground turkey for the ground beef;
Add an extra cup of water if you like a thinner soup (this soup has a thicker, chili-like consistency);
Use diced tomatoes with green chilies instead of the regular diced tomatoes if you like a spicier kick;
Garnish with your favorite toppings, or set up a "toppings bar." The options are endless, including: sour cream or Greek yogurt, sliced green or red onions, grated cheese, sliced black olives, fresh cilantro, guacamole or diced avocado, and corn chips