Melt the butter in a large pot or dutch oven over medium heat.
Add the sliced onions and cook, stirring occasionally, for 15-20 minutes until they turn a deep golden brown.
Stir in the minced garlic and cook for 1 minute.
Deglaze the pot with white wine vinegar, scraping up any browned bits with a wooden spoon.
Pour in the beef broth, Worcestershire sauce, thyme, bay leaf, salt, and pepper. Stir to combine, then bring to a rolling boil.
Add the pasta, ensuring it’s submerged in the liquid. Cover and reduce the heat to medium-low. Cook for 8-10 minutes, stirring occasionally, until the pasta is tender.
Remove the bay leaf and thyme sprigs if using fresh thyme. Stir in the heavy cream until the sauce is smooth and creamy.
Serve hot, topped with shredded provolone or parmesan cheese.