Preheat the oven to 375 degrees. Combine the ground beef, onion, garlic, ale, Dijon mustard, breadcrumbs, egg, salt, and black pepper in a large bowl. Mix until evenly blended.
Shape the mixture into a loaf and place it in a loaf pan. Bake for 40 minutes.
While the meatloaf bakes, combine the beer, brown sugar, Dijon mustard, and apple cider vinegar in a small saucepan. Simmer over medium heat for 8 to 10 minutes until the glaze thickens slightly.
Remove the meatloaf from the oven and brush the glaze over the top. Return it to the oven for 10 more minutes.
Let the meatloaf rest for 5 minutes before slicing.