Heat olive oil in a pan and add the onions, thyme, salt, and pepper and cook over medium-low heat, stirring occasionally until the onions are translucent but not brown. Off the heat, add the Worcestershire sauce, chicken stock, and tomato paste. Allow to cool slightly.
In a large bowl, combine ground beef, onion mixture, bread crumbs, and eggs, and mix lightly with a fork. Don't mash or the meat loaf will be dense. Shape the mixture into a rectangular loaf on a sheet pan covered with parchment paper. Spread the ketchup evenly on top. Bake for 1 to 1 1/4 hours,and the meat loaf is cooked through.