Add the Greek yogurt, pesto, lemon juice, olive oil, and salt to a bowl or 2-cup measuring cup. Use an immersion blender or whisk to blend the ingredients together until smooth. If the dressing is too thick for your preference, add water 1 teaspoon at a time until it reaches your desired consistency.
Pour the dressing over your salad of choice, or use it as a dip for raw vegetables or crackers/chips. Store any leftovers in an airtight container or jar in the fridge.