In a skillet, melt butter or bacon grease over low heat.
Add sliced onions and toss to coat with butter.
Sprinkle with salt and cook until golden, 15-20 minutes.
Add thyme leaves and cook for 1 more minute.
Remove from heat and set aside.
Preheat the oven to 350°F and line a baking sheet.
In a large bowl, mix ground meats, pork rinds, onion powder, pepper, and salt.
Add the egg and half of the caramelized onions. Mix well.
Shape the mixture into a loaf on the prepared sheet.
Bake for 40-50 minutes, until internal temperature reaches 160°F.
Remove from oven and top with shredded cheese and remaining onions.
Place back in the warm oven for 5 minutes to melt cheese.