Wash peppers and pat dry. Toss in a bowl with olive oil, then put in a grill basket in a single layer. Grill, turning peppers occasionally, until peppers are blackened in places and look a bit wilted, about 8 minutes.
To make the optional sauce, whisk together tahini, lemon juice, water, cardamon, and fine salt.
Place peppers in a serving bowl and sprinkle with coarse salt and black pepper.