Directions
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COMBINE all ingredients thoroughly and set aside.
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MELT butter In medium saucepan over medium heat; whisk in flour until well blended. Slowly whisk in half-and-half or milk. Continue stirring until sauce has come to a simmer and thickened. Gradually stir in cheese; when melted, add barbecue sauce and 1 tablespoon of BBQ rub. Season with salt and pepper.
 - COAT tuna steaks generously on both sides with some of BBQ rub. Transfer to plate and let stand for 15 to 20 minutes in refrigerator.
 - PREHEAT grill or cast iron skillet. Cook tuna to desired degree of doneness, about 4 minutes per side for medium (tuna will continue to cook after removed from heat).
 - TOAST bread slices lightly on both sides. Cut each tuna steak in half. Top each bread slice with piece of tuna and spoon warm cheese sauce on top.