CREATE TABLE table_13642023_2 (circuit VARCHAR(255), rnd VARCHAR(255), gtu_winning_team VARCHAR(255))
On what circuit was the GTU winning team #59 Brumos Porsche - Audi in round 5? 
    
SQL: SELECT circuit FROM table_13642023_2 WHERE rnd = 5 AND gtu_winning_team = "#59 Brumos Porsche - Audi"