Preheat the oven to 375 degress.

Heat the oil in a skillet over medium-high heat until shimmering and cook the onion, celery and garlic for about 5 minutes or until softened. Set aside to cool.

Mix together the meat, breadcrumbs, tomato paste, worcestershire sauce, 1/3 cup of ketchup and salt. Season with pepper. Add the cooled vegetables and mix well sing your hands or a wooden spoon.

Shape the meat into six patties and arrange on a baking sheet. Spread 1 TB ketchup on each burger and bake for about 25 minutes or until cooked through.

Serve tucked inside the hamburger buns.