I prefer cutting up a filet or two when wanting to cook bite sized pieces. A good sear and a stir and they are done. So a good soak in a marinade or a rub is essential for extra flavor. The filet has enough flavor for me, just salt & pepper is all I need.
I’m marinading filet mignon cubes in a teriyaki sauce right now. I will sear it under an infared broiler from the 50s and serve over in an Asian salad. We’ve adopted the philosophy of meat as an accompaniment instead of the main.