1 lb Cod/ perch or turbot fillets 1/2 c Olive oil; divided 1 cn Plum tomatoes (14 1/2-oz) ; undrained and Coarsely chopped 1 md Onion; sliced 1 cl Garlic; minced 2 tb Minced fresh parsley 1 tb Minced fresh tarragon Salt Freshly ground black pepper