In a small mixing bowl, mix all brown sugar ketchup glaze ingredients (reserving the rest of the minced onion for the meatloaf itself), stirring or whisking to combine well. Set aside.
Tear off a large strip of aluminum foil (heavy duty works well), and press it into the bottom and up two of the sides of a 6 quart or larger slow cooker. Spray lightly with non-stick cooking spray, then set aside.
Add ground beef, remaining minced onion (from step 1), stuffing mix, milk, eggs, 2 tablespoons glaze, salt and pepper. Use your hands to mix until just combined (being careful not to over mix).
Shape into an oval-like shape and place into the foil lined crockpot. Top with ½ cup of the glaze, cover, and cook on LOW for 6 hours.
When finished cooking, carefully lift out the meatloaf, using the foil overhang, and place on a baking sheet. Top with ⅔ cup of the glaze and broil until glaze is sticky and bubbly.
Serve sliced, with remaining glaze sauce served on the side for drizzling.
