Trim the leaves, then slice the cauliflower into ¾ to 1-inch thick steaks (usually 2 full steaks per cauliflower, the rest will be florets — save for later!).
pan roast cauliflower in a cast iron pan for 5 minutes, flipping halfway. This is to get a beginning sear before marinade.
Whisk marinade together.
Place cauliflower steaks in a shallow dish or sealable bag.
Brush or pour marinade over both sides.
Cover and refrigerate overnight (or at least 8 hours, no longer than 48 hours).
Remove from the fridge 20 minutes before cooking to let them come to room temp.
Brush both sides with olive oil. Season with paprika, garlic powder, onion powder, salt, pepper, and a touch of soy sauce.
Prep the grill - get it up to temperature (shoot for ~400 degrees)
In a grill safe container or in aluminum foil, put the seasoned potatoes on the grill first.
Next on the grill, sear cauliflower steaks for 10 minutes per side, until golden and cooked through (baste if desired with leftover marinade).
Transfer pan to oven and roast for 20–25 minutes, flipping halfway. (Baste with pan juices halfway if desired.)