In a medium-size mixing bowl whisk together mayonnaise, French dressing, ketchup, relish, onion, vinegar, garlic, onion powder and salt until fully combined.
Pour into an airtight container and chill for 8 hours or overnight.
Store chilled in an airtight container for up to one week.
Notes
This sauce can be made and stored in an airtight container in the refrigerator for up to one week.