Thinly slice the yellow onions about 1/4-inch thick for even caramelization.

In a large Dutch oven, heat olive oil over medium heat and add the sliced onions. Stir occasionally for 30-40 minutes until golden brown and caramelized.

Pat the chuck roast dry and generously season both sides with salt and black pepper.

Sear the roast in the pot for 3-4 minutes per side until a brown crust forms.

Pour in 1 cup of beef broth and deglaze the pot by scraping the bottom with a wooden spoon.

Return the caramelized onions to the pot and add Worcestershire sauce, dried thyme, and more beef broth as needed to nearly cover the roast.

Cover the pot and slow cook in a preheated oven at 325°F for 3-4 hours until tender.

Let the roast rest for 15 minutes, then slice or shred meat, and serve as desired.