Preheat the oven: Preheat your oven to 375°F (190°C).
Prepare the vegetables: Finely chop the onion, bell pepper, and celery. In a skillet, sauté them with a little oil over medium heat for 3-5 minutes, or until softened. Remove from heat and set aside.
Mix the meatloaf: In a large bowl, combine the ground beef (or beef and pork blend), breadcrumbs, milk, egg, sautéed vegetables, minced garlic, Cajun seasoning, Worcestershire sauce, hot sauce (if using), salt, and pepper. Mix thoroughly until well combined.
Form the meatloaf: Shape the mixture into a loaf and place it in a greased baking dish or on a lined baking sheet.
Prepare the glaze (optional): In a small bowl, mix together the ketchup, mustard, and brown sugar. Brush this glaze over the top of the meatloaf for added flavor and a glossy finish.
Bake the meatloaf: Place the meatloaf in the oven and bake for 45-55 minutes, or until the internal temperature reaches 160°F (71°C).
Rest and slice: Let the meatloaf rest for 10 minutes before slicing. This allows the juices to redistribute and ensures a tender, juicy meatloaf.