Coat the top and bottom of the tuna steak with the Asian blackening spice. Preheat a cast iron or heavy bottomed skillet on high heat until very hot, then carefully add clarified butter and place the tuna into the pan. Sear until you have formed a crust, then turn and cook the other side until similarly crusted. This should take about 1 minute per side and the tuna will be rare at this point. To cook to a higher degree of doneness, reduce the heat to medium and continue to cook on each side until it is to individual liking. Steam the asparagus and griddle the tomatoes while the tuna is cooking.