1 boneless beef chuck shoulder, arm or blade pot roast (about 2 1/2 pounds)
2 tablespoons Cajun seasoning blend
1 14 1/2-ounce can diced tomatoes with onion, undrained
1 tablespoon all-purpose flour
Press Cajun seasoning evenly onto all surfaces of beef pot roast. Place two 24- by 18-inch pieces of heavy-duty aluminum foil on top of each other in shallow roasting pan; place beef in center of foil. Bring up all sides of foil forming a bag and so no liquid can leak out; do not seal.
Combine tomatoes and flour in small bowl; pour evenly over surface of pot roast. Seal top and sides of bag with double fold.
Prepare grill for indirect cooking by igniting an equal number of charcoal briquets on each side of the fire grate, leaving open space in center. When coals cool down to medium and are ash-covered (about 15 to 30 minutes), add 3 to 4 new briquets to each side. Place aluminum foil drip pan in center of grate between coals. Position cooking grid with handles over coals, so briquets may be added as needed.
Remove foil bag from pan and place in center of grid over drip pan. Grill, covered, 2 to 2 1/2 hours or until pot roast is fork-tender. (Add 3 to 4 briquets per side every 30 minutes to maintain heat.)
Remove foil packet to clean shallow pan. Using oven mitts, cut packet open with sharp knife. Carefully fold back top of packet allowing steam to escape. Remove pot roast; let stand a few minutes before slicing. Reserve any drippings and serve along with the roast.