In a large mixing bowl, crack one large egg and whisk it lightly. Add in 2 tablespoons of ketchup, a teaspoon of prepared mustard, dry bread crumbs, and onion soup mix. Season this mixture with salt and pepper to taste. Combine these ingredients gently until they are just blended.

Incorporate 1 pound of ground beef into the mixture. Using your hands, mix until everything is just combined and form the meat into an oval loaf shape.

Place your shaped meat loaf into a non-metallic, microwave-safe dish and cover the dish with a microwave-safe lid or plastic wrap.

Microwave the covered meat loaf on high for 10 to 12 minutes, checking for an internal temperature of 160°F.

In a separate bowl, whisk together the remaining ketchup, ¼ cup of sugar, 2 tablespoons of brown sugar, and 2 tablespoons of cider vinegar.

Drizzle the sugar and ketchup mixture generously over the cooked meat loaf.

Return the covered meat loaf to the microwave and heat on high for an additional 2 to 3 minutes.

Remove the dish from the microwave and allow the meat loaf to rest for 10 minutes covered.