In a small saucepan, combine the ketchup, brown sugar, apple cider vinegar, and hot sauce. Bring it to a gentle simmer over medium heat, stirring regularly for about 5 minutes until it thickens slightly. Measure out ½ cup to brush on the meatloaf later, setting the rest aside.

Lightly coat a sheet pan with cooking spray and set it aside.

In a medium saucepan over medium-high heat, add the olive oil and chopped onion. Sauté for 5-7 minutes until the onions are fully softened. Add the minced garlic, cooking just until fragrant, about 30 seconds, then let it cool a bit.

In a large mixing bowl, combine the sautéed onion mixture with gluten-free bread crumbs, milk, eggs, Dijon mustard, Worcestershire sauce, salt, pepper, thyme, and parsley. Stir everything together until well mixed.

Add in the lean ground beef and ground pork. Use your hands to knead the mixture until all the ingredients are thoroughly combined, ensuring a tender meatloaf.

On the prepared sheet pan, form the meat mixture into a long, flat rectangle about 9×5 inches in size.

Place the meatloaf on the upper rack of your oven and broil for about 5 minutes until the top is nicely browned.

Brush ¼ cup of the prepared glaze over the top and sides of the meatloaf, then broil again for about 2 minutes until the glaze caramelizes a bit.

Now, brush the meatloaf with another ¼ cup of glaze. Set your oven to 350°F and bake for 40-45 minutes, or until a meat thermometer reads 160°F for perfectly cooked meatloaf.

Once done, transfer the meatloaf to a serving platter and tent with foil, allowing it to rest for 20 minutes. Then, slice it up and serve it warm with the reserved glaze for dipping.