First preheat the oven to 400 degrees and place the cast iron in the oven as it’s heating up. The cast iron should have a small spray of oil on top, or should be seasoned well.
Next, wash the eggplant. Dry it, and cut it in half lengthwise. When the oven is good and hot, place the eggplant in the cast iron.
Roast for about 30 minutes (check it at 25 minutes, in case you have smaller eggplant, they can be done sooner)The top should have softened up, but the eggplant should still have a shape. You should be able to easily pierce the eggplant with a knife.
Remove the eggplant and cut it into cubes or simply score the eggplant steak. This reveals some crevices that would easily be filled with some type of sauce, like this cilantro chutney.