In large skillet over medium high heat, brown ground beef with chopped onion and bell pepper until meat is slightly browned and crumbly, about 10 minutes. Add minced garlic, stir, and cook for a couple more minutes. Add mixture to large slow cooker.
Fill a sauce pan with about 4 inches of water and bring to a boil. Score tomatoes on top and bottom with sharp knife and toss them in the boiling water for about a minute or two until the skins start to peel away. Use hands to remove peels and seeds from tomatoes, then crush and add to slow cooker.
Stir in remaining ingredients. Set slow cooker to low and cook for 4-8 hours.
Alternatively, meat can be browned in electric pressure cooker, remaining ingredients can be added, and chili can be cooked on high pressure for 20 minutes.
Garnish with freshly grated sharp cheddar, sour cream, and sliced green onions.