Preheat your oven to 425 degrees
Slice the onions in half, remove the peel and trim back the base to clean it up, but leave enough to hold the onion halves together
Place the onions cut side down into an oven safe skillet and set aside for now
Place 2 cups of beef broth into a small sauce over medium high heat and bring to a boil
As soon as the broth is boiling, remove from the heat and whisk in 4 tablespoons of butter, 1 tablespoon of soy sauce, 1 tablespoon of tomato paste and 1 teaspoon of worcestershire sauce until everything is fully combined
Place the onions into the broth cut side down and cover the skillet with foil
Bake the onions covered for 30 minutes in a 425 degree oven and then carefully transfer the skillet out onto a heatproof surface
Remove the foil and carefully flip the onions cut side up
Spoon the sauce over the onions and place them back into a 425 degree oven
Bake uncovered for another 40 minutes basting the onions every 10 minutes
Serve with crusty bread and garnish with finely shredded Gruyère and fresh thyme