Juice 1 medium lemon until you have 2 tablespoons. Add the juice, 1 garlic clove, 1 1/4 cups plain Greek yogurt, 1/4 cup olive oil, 2 tablespoons tahini, 1/2 teaspoon kosher salt, and 1/4 teaspoon white pepper to the blender. Blend until the mixture is creamy and smooth, 45 seconds to 1 minute. Place the blender in the refrigerator (or you can transfer the soup to a bowl) and chill for at least 4 hours and up to overnight.
