Step 1: Preheat your oven to 350°F (175°C). Lightly grease a 9x5-inch loaf pan or a baking sheet if free-forming the meatloaf.
Step 2: In a large mixing bowl, combine the ground beef, beaten egg, milk, crushed saltine crackers, Lipton Onion Soup Mix, chopped onion, green bell pepper, garlic powder, black pepper, and salt.
Step 3: Using your hands, gently mix all the ingredients until just combined. Be careful not to overmix, as this can lead to a dense, tough meatloaf. The mixture should still be moist but hold together.
Step 4: Transfer the meat mixture into the prepared loaf pan, gently pressing it evenly, or shape it into a loaf on the prepared baking sheet.
Step 5: In a small bowl, whisk together the ketchup, brown sugar, yellow mustard, and apple cider vinegar to create the glaze.
Step 6: Spread about half of the glaze evenly over the top of the meatloaf.
Step 7: Bake for 1 hour at 350°F (175°C). After 1 hour, remove the meatloaf from the oven and spread the remaining glaze over the top. Return to the oven and bake for an additional 15-20 minutes, or until an internal temperature of 160°F (71°C) is reached.
Step 8: Once cooked, remove the meatloaf from the oven and let it rest for 10-15 minutes before slicing and serving. This allows the juices to redistribute, ensuring a moist and flavorful result.