Yep, no gasket there, just two thick, flat machined flanges. I would scrape them clean with a razor blade and wash them with solvent and you should be fine re-assembling them dry. Or if you want to be really sure they are going to seal, carefully flat-file them until the file evenly scrapes the entire surace to flatten it, or alternatively have a machinist kiss off small amounts with a mill until the fresh machined surfaces are totally flat.
Be sure to use a copper-based anti-seize liberally on the turbo mounting bolt threads, if you want them to come off more easily next time. (In my experience this is the one place where the grey moly-type antiseize can't take the heat; it dries up leaving a crusty powder!)