Sausage Zucchini and Spinach Soup

bulk italian sausage ((if using sausage links, remove from casing))

large red onion (, diced)

chopped celery

small cloves garlic (, minced)

crushed fennel seed

garlic powder

medium zucchini (, diced)

tomato paste

of crushed tomatoes

water ((more or less depending on how soupy you want it))

( 5 oz) bag of baby spinach, roughly chopped

salt