I've seen a recipe using a sweetener instead of sugar for caramel. I'm wondering what kind of sweetener would actually work for this - the recipe didn't specify.  Various sweeteners I've seen in the shop are pretty different:   50% sugar "sweetener" Saccharine based Stevia extract ...   What process am I actually looking at when making a (...) + butter + sour cream caramel? What ingredient makes it possible? 
The only non-caloric sweetener that I knew of that is chemically similar to sugar, and so might have a chance at caramelizing was sucralose. ... but everything that I've read up on it says it's heat stable (but that might just be at baking temperatures).  Searching for 'sucralose caramel', I was able to find a few recipes, but they all seem to be using a mix of sucralose and some other sugar.  ("Splenda Sugar Blend for Baking" is not pure sucralose)   https://web-website-spa-production.production.yummly.com/recipe/Low-Carb-Chewy-Honey-Caramels-1567333?prm-v1 https://sucralose.org/caramel-sticky-buns/   But that search also found:   https://www.wholesomeyum.com/recipes/sugar-free-caramel-sauce-recipe-low-carb-keto/   ... which uses "Surkin Gold", which is erythritol, derived from glucose.  So I suspect it's possible to replace some of the sugar with sugar-derived non-caloric sweeteners, but you may need to experiment with exactly how much you can get away with, and may need to tweak your process slightly. 