Laurent Tourondel is planning to open an American-style brasserie in the summer in Cassa Hotel and Residences, 70 West 45th Street. Details of the restaurant, including its name, has not been decided, but there will be about 150 seats and it will be open for breakfast, lunch and dinner. Mr. Tourondel was once partner in the BLT restaurants but now remains involved only with BLT Market in the Ritz-Carlton Central Park. He also owns a burger place, LT Burgere, in Sag Harbor, N.Y.