Slice four large yellow onions into thin half-moons. Heat 2 tablespoons of olive oil in a Dutch oven over medium heat. Add the onions and cook for 30–40 minutes until golden and caramelized.

Season a 3-4 pound beef chuck roast with salt and pepper. In the Dutch oven, increase heat to medium-high and sear the roast for 4-5 minutes on each side until nicely browned.

Layer the caramelized onions evenly over the seared roast. Pour in 1-2 cups of beef broth to cover the bottom of the pot.

Cover the Dutch oven and place it in a preheated oven at 300°F (150°C). Cook slowly for 3 to 3.5 hours.

Remove the pot from the oven. Preheat the oven's broiler, layer 1-2 cups of grated Gruyère cheese on top, and broil for 2-5 minutes until bubbly and golden.

Let the pot roast rest for 10-15 minutes covered loosely with foil before serving.