My fave LCHF salad and coleslaw dressing is apple cider vinegar (ACV)mixed with a no-sugar added aioli mayo. Or in the rare times I don't feel like garlic - a no-sugar added plain mayo.
I also make my own mint sauce with apple cider vinegar - another great way to get as much ACV into me as possible. And it tastes wonderful in condiments.
Heinz are doing a "no added salt and sugar" tomato ketchup these days (I found it in Sainsbury's but everyone seems to do it ) which comes in at 5.7g carb per 100g weight, or less than 1g per 15g portion. Works for me within my standard 20g/day routine.
I'm a vinaigrette person, Good olive oil (sometimes smoked garlic infused), vinegar of choice, red/white wine, cider and sometime wholegrain mustard, never been fond of mayo/salad cream. (2 parts oil, 1 part vinegar)
If I'm frying meat, such as a steak, I like to add double cream to the meat's residue, it takes literally seconds for the cream to thicken. Adding quite a bit of crushed black peppercorns is a good favourite, adding cheese especially blue cheese is another favourite.
Can also add home made stock (previously prepared and frozen for convenience) and thicken with liquefied veg, or if you can afford the carbs, a small teasp of cornflour.