Edit the recipe and tap the picture at the top left. Choose Photo Library, Camera (Enable Camera Access until you’ve allowed it), Recipe Website for pictures from the page it came from, Search for Images, or Paste From Clipboard. Remove Photo takes it off.
Recipe Website shows only for a recipe saved from a website, and Search for Images once the recipe has a name.
Search for Images looks for pictures of the recipe’s name. Change the words at the top and search again if you like, then tap a picture to use it. Turn on Remove Background first if you want the picture without its background.
On devices with Apple Intelligence, Create with Image Playground makes a picture from the recipe’s name.
Recipes from websites with no photo? Tap your picture at the top left, then Settings, and under Import & Export tap Get Photos from Recipe Websites, then Get Photos. Menu Planner 2 opens each recipe’s web page and adds its picture. Keep it open until it’s done; with a lot of recipes it can take a few minutes. Stop keeps the photos added so far, and Try Those Again tries the websites that didn’t answer.
Using a picture from Search for Images is a Premium feature. Get Photos from Recipe Websites is free.