Italian Sausage and Cabbage Soup

Mild Italian Sausage, removed from casing and crumbled

olive oil

medium or 1 extra large onion, halved and thinly sliced

to 6 medium cloves garlic, finely chopped

medium carrots, cleaned and cut into 1/4" rounds

head green cabbage (about 2 pounds), core removed and shredded

kosher salt plus a couple pinches

freshly ground black pepper

diced tomatoes (unsalted)

chicken stock or broth

crushed red pepper flakes for serving (optional)

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