I added a can of San Marzano tomato puree instead of diced. It's in the slow cooker. How can I thicken it up? Thank you!!!! (Other ingredients already in include seasoning, black beans, onion, turkey corn and peppers)
You may either cook the chili down for longer which will keep reducing the liquid or you can add a roux (flour and fat sauteed on the stove and then whisked into your chili) or add some cornstarch to some chili liquid and then add that back to the chili. Good luck!
I would thicken with a tablespoon or two of tomato paste.
You could also mash up some black beans to thicken.
You've received great advice so far. But I have to add that a slow cooker is not the best vehicle for it---especially when you are cooking something as lean as turkey. The cornstarch mentioned above is called a "slurry" and it should help. But the best vessel is a well seasoned cast iron pot with the lid only partially covering.