Canned fire-roasted tomatoes add heat to this big-batch recipe. For best results, reheat the leftovers on the stovetop for 10 to 15 minutes.
In a 4- to 6-quart slow cooker, combine the beef, tomatoes, beans, zucchini, onions, tomato paste, garlic, chili powder, oregano, 1½ teaspoons salt, and ½ teaspoon pepper.
Cover and cook until the vegetables are tender and the meat is cooked through, on low for 7 to 8 hours or on high for 4 to 5 hours (this will shorten total recipe time).
Reserve half the chili for tomorrow’s dinner. Serve the remaining chili with the sour cream, avocado, and cilantro.
Reheat and serve: Reheat the chili in a large saucepan over medium-high heat, stirring occasionally, for 10 to 15 minutes.