01 -
Preheat your oven to 350°F (175°C).
02 -
Melt butter in a skillet over medium heat. Sauté sliced onions until caramelized and golden brown, about 20-25 minutes. Add beef broth to deglaze, stir until absorbed. Let cool.
03 -
In a large bowl, combine ground beef, breadcrumbs, milk, garlic, egg, Worcestershire sauce, Dijon mustard, thyme, salt, and pepper. Mix well.
04 -
Fold in the cooled caramelized onions and half of the Gruyère cheese. Shape into a loaf and place in baking dish.
05 -
Bake for 1 hour or until internal temperature reaches 160°F (70°C).
06 -
Sprinkle remaining Gruyère cheese on top and bake 5-10 minutes more until cheese melts and bubbles.
07 -
Let meatloaf rest 10 minutes before slicing.