This recipe easily scales up so make more if you are serving corn on the cob for a crowd. The corn may be cooked any way you desire, but for the most authentic street corn experience, it should be grilled or roasted until lightly charred.
Whisk together the first 5 ingredients. Let sit for 15 minutes. Remove garlic clove before serving if desired (I do not mince the garlic, because this way the garlic infuses the sauce without upsetting my stomach as raw garlic is wont to do).
Run a lemon wedge over the freshly boiled, roasted or grilled cob of corn. Schmear 1-2 tablespoons of the yogurt sauce over the corn. Sprinkle with the sumac powder and coarse or flaky sea salt. Serve immediately.