Remove filets from fridge and season to taste with salt and pepper, let come to room temperature
Pre-heat oven to 400 degrees
About 15-20 minutes before cooking filets, place cast iron skillet into oven
Remove hot pan from oven, place on burner over medium high heat, add some cooking oil, I typically use a little avocado oil plus butter
Once butter has melted, place steaks into sizzling hot pan and let sit for 7-8 minute, until it develops a nice brown crust
Turn steaks over and place pan into oven, using a glove or towel, for another approx. 7 or so minutes
For medium rare Filet Mignon, remove steaks from oven when internal temperature reaches about 120 degrees, they will rise a few more degrees after taking them out of the oven