Brush the tuna steaks with the olive oil and season with salt and pepper.
Grill, broil, or pan fry to desired degree of doneness.
Combine the sauce ingredients in an electric blender or food processor and process until smooth. Omit the mustard if you dont want the bright colour.
Spread a tablespoon (15 ml) of the sauce on each tuna fillet after they have finished cooking and serve immediately, with additional sauce on the side.