Yes, I am aware of just almost exactly how many French dressings I have posted to this here interwebs thingy…
There is your Catalina, your Western style, your ‘Fresh‘ (tho’ that’s not one of my favorites), and myriad other variations. But, I don’t recall any of the others calling for mayonnaise!
The mayo does impart an extra creaminess, but, mebbe more importantly, it cuts way back on the sugar required.
Julia Child once famously observed that “fat gives things flavor” – and, if you think about it, you’ll notice that many ‘lite’ products replace natural fats with sometimes not so natural sweeteners and such. I automatically 
cut any sugar called for in salad dressing recipes I come across back by at least one half; for this recipe, I cut it back to about 1/12th of what was listed, and still ended up with a fine tasting dressing.
The original recipe I came across also called for none of the traditional seasonings that go into a ‘French’ salad dressing, but I took care of that, and the finished product?
Tasty!
INGREDIENTS
Creamy French Dressing:
•1/2 cup mayonnaise
•1/2 cup ketchup
•1/4 cup apple cider vinegar
•1/2 cup diced sweet onion
•1 tsp sugar
•1 tsp paprika
•1/2 tsp dry mustard
•1/4 tsp salt
•1/4 tsp black pepper
•1/2 tsp garlic powder
•1/4 cup salad oil
Bonus! Special Sauce:
•1/4 cup mayonnaise
•2 tbsp creamy French dressing
•1 tbsp chop pickle (or relish)
•1/4 tsp dried onion
•1/4 tsp sugar
•1/8 tsp Aleppo pepper
•1/8 tsp black pepper
Add the sugar, paprika, dry mustard, salt, garlic powder and black pepper to a blender jar along with the sweet onion and vinegar. Add the mayonnaise and ketchup, then pulse to blend and finely chop the onion.
With the blender running, slowly stream the oil in through the opening in the lid and continue to blend until it has been absorbed into the dressing.
Transfer to a covered jar and stash in the fridge until needed.
Note: this dressing is quite nice right away, but better if allowed to rest for a couple of hours before using.
Now, for the bonus!
Looking for a little sumpin’ sumpin’ extra to slather on your burgers? Well, try this special sauce, made with a bit of the creamy French dressing, a bit more mayonnaise, and other good things.
Simply stir together the creamy French dressing, the mayonnaise, chop pickle, dried onion bits, and the seasonings, then stash in a covered jar in the fridge for a couple of hours – this will help the dried onion to absorb a bit of the extra liquid in the sauce and to spread the flavor around.
Serve on burgers or really most any sammich where you’d add plain mayonnaise.