Make meatloaf: Preheat oven to 400ºF. Line a large rimmed baking sheet with foil. Combine onions, pepper, ketchup, mustard, breadcrumbs, eggs, Worcestershire, oregano, and thyme in a bowl. Season with salt and pepper. Gently mix in beef with your hands, being careful not to overmix. (It should be soft but hold its shape.) Transfer meat to prepared baking sheet and shape into a 10-by-5-inch loaf.