In a large pot of boiling salted water cook fettucini till al dente.
While pasta is cooking .heat a skillet over medium heat and add oil.
saute onion and garlic until soft but not brown.
Meanwhile in a small bowl mix cornstarch and lemon juice, mix well, then add chicken broth or stock.add this mixture to the onions along with the tuna, oregano,pepper flakes salt and pepper --.