If using ribeye, follow same instructions as chicken in Steps 1 and 3, searing until browned on one side, 2-3 minutes, then roasting seared side up until steak reaches minimum internal temperature, 12-14 minutes. Rest, 3 minutes. Halve to serve.
If using mahi-mahi, pat dry, halve, and season with a pinch of salt and pepper. Follow same instructions as chicken in Step 3, searing until mahi-mahi reaches minimum internal temperature, 3-4 minutes per side. No need to roast in oven.