Preheat to 425 degrees and arrange one oven rack just under the broiler and one on the lowest position.
Pour 2 tablespoons oil into a small bowl.
Squeeze the juice of half of the lemon into the bowl.
Add the mustard, honey, garlic, tarragon, sun-dried tomatoes, and capers to the dressing and whisk with a fork. Set aside.
Place head of cauliflower on a cutting board and cut off the stem and leaves.
Stand the cauliflower upright on a cutting surface.
Using a very sharp knife, cut slices by cutting straight through cauliflower beginning at one side and moving towards the center and through to the other side. Cut ½ - ¾ inch slices. You should end up with 2-3 intact “steaks” and smaller pieces of florets.
Place the cauliflower on a sheet pan lined with foil for easy clean-up.
Drizzle 3 tablespoons of olive oil over the cauliflower, season with a bit of salt and pepper.
Using a brush or your fingers, coat the steaks and florets with the oil.
Place baking pan on lowest level of oven and bake for 15 -20 minutes, or until the underside of the steaks are well browned.
Remove pan from oven and carefully flip the pieces of cauliflower over.
Put pan back into the oven and bake for 10 minutes.
Remove pan from oven, turn broiler on, and turn over the cauliflower one more time.
Sprinkle half of the grated parmesan over the cauliflower and place under broiler for a few minutes until the veggies and cheese are lightly browned.
Serve the steaks whole or cut in half lengthwise, depending on how many intact steaks you have and how many people you are serving. I like to serve this dish plated with a full or half steak on each plate and some smaller florets arranged around the larger piece. Spoon some of the dressing over the cauliflower and serve with a wedge of lemon. Season with more Parmesan, salt and pepper.