1Caramelize chopped onions with 3 Tbsp butter, 3 Tbsp Worcestershire sauce, and salt for about 20 minutes.
2Set caramelized onions aside.
3Mix ground beef, panko, 3 Tbsp Worcestershire sauce, eggs, Italian seasoning, smoked paprika, salt, and pepper.
4Form a meatloaf, create a pocket in the center, add caramelized onions and shredded Gruyère cheese. Top with remaining meat mixture, cheese, and onions.
5Place in smoker at 350 degrees until the internal temperature reaches 160 degrees (approximately 1 1/2 hours).