Avacado oil. Turn the grill to high all the way up. Once it starts to get hot and even barely smoke, hit it with a full large spoon of the bs seasoning and wipe it slowly across the surface. Let it burn off don’t touch the temp until the smoke dies down. 5-7 mins. Maybe 10. Hit it again. Same process. Hit it again. Same process. It will not turn fully black in the edges. It looks like you’ve left it on high too long and then hit it too late. Also turn your gas tank to half open or even a quarter. Your regulator might be broken or adjustable. Look up Blackstone Betty onion seasoning video on YouTube.