Heat a skillet over medium heat. Form small sausage balls by pressing the sausage together with your hands and dropping them into the hot pan (see picture). Cook in two batches, browning all sides and cooking through completely. Remove to a paper towel-lined plate. Sauté the onions in the leftover pork fat until soft, about 8 minutes. Add the pressed garlic and sauté for 30 seconds more.
Meanwhile, in a large, heavy-bottomed soup pot, combine the chicken stock, diced tomatoes, tomato paste, oregano, basil, sugar, chili peppers, pepper, and salt. Bring to a boil. Add the onion-garlic mixture and simmer uncovered for 10 minutes. Use a potato masher to lightly crush the tomatoes and onions into the soup. You won’t be able to mash much, but a little is fine.
Add the tortellini and cook according to package directions, usually 7-9 minutes. Stir in the cooked sausage and spinach until the spinach just wilts. Serve immediately.
