Preheat your oven to 375°F (190°C). Gather your ingredients and prepare your workspace.

In a large skillet over medium heat, add olive oil and cook thinly sliced onions for 15 to 20 minutes until golden brown.

In a mixing bowl, combine ground beef, cooled caramelized onions, breadcrumbs or almond flour, eggs, and a splash of milk or broth. Season with salt and pepper, then mix gently.

Mold the mixture into a loaf shape and place it in a greased baking dish. Create a slight well in the center for even cooking.

Top the meatloaf with shredded Gruyère cheese and bake for 50 to 60 minutes or until the internal temperature reaches 160°F (71°C).

Remove the meatloaf from the oven and let it rest for 10 minutes before slicing.