Door seal to stop spreading cooking odour
You'd essentially use the type of weather stripping commonly seen on exterior doors. Foam tape, rubber bead gaskets, brass compression strips, bottom sweeps, etc. Which you use is up to you. 

I think you'll end up disappointed, though. If odor is escaping even with your exhaust fan running and creating negative pressure, something is moving it around. Sealing that door probably won't yield satisfactory results.