From here. I added a bit of extra vinegar because I found it too sweet. Probably should have started at 4 Tbsp. splenda and tasted it 🙂 It does taste like I remember bottled russian dressing tasting. I had it over romaine with ham for a supper salad.
6 tablespoons generic splenda
1/4 cup plus 2 teaspoons white vinegar or apple cider vinegar
1/2 cup oil (I suggest a vegetable oil like soy or canola since olive oil hardens in the refrigerator)
1/2 cup low carb ketchup
1 1/2 teaspoons celery salt, or 1 tsp. salt + 1/2 tsp ground celery seed
1/2 teaspoon paprika
Pinch celery seed

Put all of the ingredients in a jar or bowl and blend well with a stick blender. Keep refrigerated. You will need to stir it well before using.