In a large bowl, combine beef stock, red wine vinegar, onion, peppercorns, bay leaves, and garlic to create the marinade.
Submerge the beef roast in the marinade, cover, and refrigerate for 48 hours, turning occasionally.
After marinating, remove the beef and pat dry. Strain the marinade and reserve the liquid.
Preheat your oven to 325°F (163°C).
Season the beef with salt and then brown it on all sides in a Dutch oven with butter and olive oil over medium-high heat.
Once browned, add the reserved marinade liquid to the Dutch oven, bring to a simmer, cover, and place in the oven for 3 hours or until the meat is tender.
For the Keto Spaetzle, mix almond flour, psyllium husk, baking powder, and salt in a bowl.
Beat the eggs, heavy cream, and water together and combine with the dry ingredients to form a dough.
Bring a pot of salted water to a boil. Using a spaetzle maker or a colander with large holes, press the dough through into the boiling water.
Cook spaetzle until they float to the surface, then remove with a slotted spoon and set aside.
Once the beef is tender, remove it from the Dutch oven and let it rest.
Bring the sauce in the Dutch oven to a simmer and whisk in xanthan gum to thicken.
Slice the beef and serve with Keto Spaetzle, topped with the thickened sauce.