In a small bowl, mix together the tomato puree, brown sugar and mustard; stir until the brown sugar has dissolved.
In a large mixing bowl, mix the eggs, minced onion, capsicum, garlic powder, cracker crumbs, salt and black pepper; mix in the mince and half the tomato puree mixture, stirring until the meat loaf is thoroughly combined. Place the meat mixture into a microwave-safe baking dish. Spread the remaining tomato mixture over the meat loaf.
Cook in microwave oven on High setting until set, the juices run clear and meat is no longer pink inside, 10 to 15 minutes depending on power of microwave oven. Drain any grease from the dish as soon as loaf is cooked; allow to stand uncovered for 10 to 15 minutes before serving.