If your scallion is not already chopped, finely chop 2 tbsp fresh scallion.
In a small bowl, add 2 tbsp light mayonnaise and 2 tbsp fat free plain Greek yogurt (use full fat yogurt if following Keto and check the mayonnaise label for Keto if needed).
Add the chopped scallion to the bowl.
Stir everything together until smooth and evenly combined.
Taste and season with salt and fresh pepper to your preference.
Cover and refrigerate before serving if desired. Store in the refrigerator in a covered container and use within about 2 days.