In a large non adhesive pan, heat olive oil over medium high heat.
Add shallots and capers and cook 7 to 10 minutes, until lightly caramelized and crisp, stirring occasionally.
Transfer to a paper towel.
Add butter to pan and a dash of olive oil if necessary.
Season the fish and sear over medium high heat until you get a coloration.
Then, reduce to medium-low and cook for 8-10 minutes (for tick-cut halibut) or 4-5 minutes (for cod or turbot filets), until the fish is cooked, depending on the thickness of the fish selected.
In a small bowl, combine shallots and capers, parsley and balsamic vinegar.
Serve over fish, sprinkle with grated lemon zest and serve with seasonal vegetables.