Form the ground beef into 4 approx 1/3 lb burger patties.
Add oil to the bottom of a small heavy bottomed pan. I use a cast iron. Place on the heated grill or on the stove on medium heat.
Add onions and cook, without stirring, until soft and caramelized, about 15 minutes.
Meanwhile, add the blackened seasonings to a plate and press the burgers into the seasoning, crusting all over including the sides.
Spray both sides of the burger patties with non stick spray. This helps the seasoning caramelize.
Heat the grill or a grill pan on the stove over medium heat.
Grease your grill grates and add all the patties.
Close the grill cover and grill for about 5 minutes each side (medium).
Add a tablespoon of bleu cheese crumbles to each patty and close the cover for an minutes to let if warm and melt slightly.
I also like to spray my buns and add them to the grill then to warm up.
To plate: add the bottom bun and top with a lettuce leaf and thick sliced tomato. Add two grilled burger patties. Then top with caramelized onions and add the top bun. Secure with a skewer or steak knife and serve warm.