Prepare the rice noodles according to pack instructions, then refresh under cold running water. Drain and toss with the coriander, vinegar and soy sauce. Set aside.
Mist the asparagus and tuna with cooking spray and season with a pinch of salt. Cook on a heated pan about 4 minutes, turning the asparagus occasionally and the tuna once, until the asparagus is tender and the tuna is medium-rare.
Brush each side of the tuna with 1/4 tsp hoisin sauce and cook for a few seconds each side until glazed.
Slice the tuna, drizzle with the remaining hoisin sauce and sprinkle over the sesame seeds. Serve with the asparagus and noodles.