3 slices bread (I make my own, but you can use whatever safe option you have)
1 large carrot
1 celery stalk
1 small onion
2 cloves garlic, peeled
1/2 cup fresh flat-leaf parsley, leaves only, loosely packed
1/2 cup plus 3 tablespoons ketchup
4 1/2 teaspoons dry mustard (mustard powder)
8 ounces ground pork
8 ounces ground veal
8 ounces ground round
2 teaspoons salt
1 teaspoon freshly ground pepper
1/2 teaspoon chopped fresh rosemary, plus a pinchful for sprinkling on top (skip the pinch on on top if you are using dried)
2 tablespoons dark-brown sugar
1 small red onion, cut into 1/4 inch-thick rings
1 Tablespoon olive oil
Preheat oven to 400 degrees.
Trim crusts from bread, grate finely or process until fine crumbs form, about 10 seconds. Transfer breadcrumbs to a large mixing bowl.
Place carrot, celery, yellow onion, garlic, and parsley in the bowl of the food processor. Process the heck out it, until vegetables have been minced, about 30 seconds, stopping to scrape down the sides of the bowl once or twice. If you leave the veggies too big, the meatloaf will be crunchy…not cool. Transfer vegetables to bowl with the breadcrumbs.
Add 1/2 cup ketchup, 2 teaspoons dry mustard, pork, veal, beef, salt, pepper, and chopped rosemary. Using your hands, knead the ingredients until thoroughly combined, about 1 minute. Wash hands like you have OCD.
Set a wire baking rack onto a parchment or foil-lined cookie sheet. Cut a 5-by-11-inch piece of parchment paper or foil, and place over the center of rack to prevent meatloaf from falling through. Using your hands, form an elongated loaf on top of the paper/foil.
Place the remaining 3 tablespoons ketchup, remaining 2 1/2 teaspoons dry mustard, and brown sugar in a bowl. Mix until smooth. Using a pastry brush, generously brush the glaze over loaf.
Place pan in the oven and bake for 30 minutes.
In the meantime, thinly slice the red onion. Place in a small bowl with the 1 T of olive oil and the pinchful of rosemary. After 30 minutes, spread the mixture over the top of the meatloaf.
Return meatloaf to the oven and continue baking loaf until an instant-read thermometer inserted into the center of the loaf registers 160 degrees…about 25 minutes more. Let meatloaf cool on rack for 15 minutes before cutting.