Place sliced onion rings in a medium bowl. Add just enough buttermilk to submerge the onions. Place in the refrigerator to soak for 2 hours.
While the onions are soaking in the buttermilk, make the flour coating. Pulse the panko bread crumbs in a blender for a few seconds until they are a finer consistency. Then, combine flour, panko, salt, pepper, seasoned salt, garlic powder, and paprika in a large bowl. Mix well and set aside.
Add frying oil to a large heavy-bottomed pot, about 1/3 full. Heat oil until it reaches about 350-375 degrees F. While oil is heating, and working in small batches, add the soaked onion rings to the flour mixture. Toss to coat the onion rings in the flour. Shake off excess flour and transfer to a plate. Continue until all onion rings are coated.
Carefully add the coated onion rings to the hot oil in small batches. Fry until golden brown on all sides. Remove from the oil with a strainer and transfer fried onion rings to a wire cooling rack or paper towel set on top of a baking sheet.
Preheat griddle to a temperature of about 350 - 375 degrees F.
While onion rings are frying, cook bacon on the griddle until done to your liking. When bacon is done, remove from the griddle and set aside. Adjust the griddle temperature to about 425 degrees F.
Portion the ground beef into 4 equally sized, loosely packed balls. *You can use a 1/3 cup measuring cup for the perfect amount of beef, then roll into a ball.
When the griddle is hot, place the beef balls on the griddle surface, making sure that you have enough space to smash and flip the patties. Immediately smash the balls as you would for smash burgers. Season the top side with your favorite burger seasoning, or salt and pepper.
Toast the burger buns on the griddle, cut side down, while the burgers continue to cook. When buns are done toasting, remove them from the griddle.
When burgers are a bit more than halfway cooked through (and there are still some pink spots on top), use a spatula or scraper to flip the burgers to the second side, making sure to scrape under the burger crust to remove it from the griddle with your burgers.
Immediately after flipping the burger patties, top each with one slice of cheese. When the cheese is melted (probably less than 1 minute), stack two burger patties on top of each other to make two double smash burgers. Immediately remove from the griddle and allow to rest for 1-2 minutes.
Build your cowboy burger - Add barbecue sauce to the bottom bun. Top with the double cheeseburger, cooked bacon strips, and homemade onion rings. Add more bbq sauce if you wish. Serve warm and enjoy!