Tomato Glaze: Mix together 1/3 cup soup, ketchup, brown sugar and 1 1/2 tsp mustard until smooth. Set aside.
Preheat the oven to 350°F. Line a standard size rimmed baking sheet pan with heavy duty aluminum foil, spray with cooking spray.
In a medium skillet saute the diced onions and peppers in a few drizzles of olive oil over medium-high heat until softened and translucent around 3 minutes. Season with 1/4 tsp salt and 1/4 tsp black pepper, then set aside to cool slightly.
While vegetables cook in a medium mixing bowl mix together beef, Panko, 3/4 cup soup, buttermilk, eggs, mustard, Worcestershire, barbecue seasoning, 1/4 tsp salt and 1/4 tsp black pepper. Add cooled peppers and onions. Mix well.
Using your hands roughly form the meat mixture into a loaf shape in the bowl. Slide the loaf onto the center of prepared baking sheet.
Pat the meatloaf into an oblong loaf shape approximately 2 1/2 inches thick. It's important to make the loaf proportional so it will cook evenly. Pour half of the glaze over the top.
Bake for 55 minutes. Remove from the oven drizzle with remaining glaze.
Return the meatloaf to the oven and bake for another 10-15 minutes or until juices run clear.
Rest on the counter for 15 minutes before serving.
Notes
Protein - Quality ingredients result in a moist and flavorful meatloaf. Use the best ground beef for the mixture. You could also adapt this meatloaf recipe using a combination of pork and beef or ground turkey.
BBQ Seasoning - You can use your favorite barbecue seasoning in this recipe. They will have differing amounts of sodium, so you can add more or less salt to suit your taste.
Breadcrumbs - Some Southerners like to use crushed saltine crackers as a binder in classic meatloaf. Others may use fresh bread crumbs, crushed ritz crackers or quick cooking oatmeal. I use panko in the recipe, and it works beautifully.
Onion - It's ideal to use a white onion or sweet Vidalia onion for the filling as a yellow onion has a more robust flavor.
Bell Peppers - You can use red bell pepper or yellow bell peppers.
Glaze - The sweet tomato glaze made with ketchup, makes it a spectacular choice for eating later as a sandwich. Use the brand of ketchup for the glaze that you already enjoy.
Optional Pan - If you use ground beef with a higher fat content (ie. 80/20) the meatloaf should be prepared in a baking dish or loaf pan to keep its shape.
Test for Doneness - You can use a meat thermometer to check the meatloaf for doneness. Insert into the thickest part of the center looking for 160°F.