Heat the olive oil in a skillet over a medium heat. Add the sausages to the skillet. Pan-fry the sausages until cooked through, no longer pink inside and browned all over. Set aside and keep warm while you prepare the gravy.
Thinly slice the onion. Add the onion to the skillet used to cook the sausages. Sweat gently over a low heat for a few minutes until tender and fragrant.
Add the paprika, tomato paste, salt, pepper and garlic powder to the skillet. Finely chop the rosemary and add to the pan. Stir well to combine and heat through for a minute.
Add the chicken stock to the skillet and bring to a boil. Stir well. Reduce to a simmer and sprinkle over the xanthan gum. Stir the gum into the gravy to dissolve. Simmer for a few minutes to thicken and reduce the gravy to your preferred consistency.
Remove the skillet from the heat. Stir the cooked sausages into the gravy, so they are well coated. Serve hot with your preferred Keto sides.