Heat olive oil in a medium sized pan and add the onions, salt, pepper and thyme. Sauté the onions until soft and lightly golden. Turn the heat off and stir in the tomato paste, Worcestershire sauce and chicken stock. Let them cool slightly.
In a large bowl, add the ground beef, breadcrumbs, eggs, ketchup, salt, and pepper. Add the cooled onions and mix gently until just combined.
Shape the mixture into a loaf and place it on a parchment paper lined sheet pan. Spread the ketchup evenly over the top.
Place it into the center rack of the oven for about 1 to or until the internal temperature reaches 160°F. Let it rest for 10 minutes before slicing.