Mahi Mahi with Caponata Sauce

Light fish, bold vegetables, and a sweet–tangy caponata come together in this Mahi Mahi with Caponata Sauce, bringing a sunny, Mediterranean feel to your table.

I’ve just come back from a wonderful week in Sicily, filled with emotions. I finally spent time with relatives and friends I hadn’t seen in seven years, and I showed my kids places tied to my childhood that they had never seen before.

To celebrate this moment, I wanted to share a Sicilian recipe. In Sicily, Mahi Mahi is called capone. It was once the main ingredient of one of the island’s most famous dishes, caponata.

Not many people realise this, but the caponata we know today began as a fish dish enjoyed by the wealthiest Sicilian families.

Over time, the fish was replaced with eggplant, which was easier to find and far more affordable. The name caponata stayed, taken from the fish itself, capone.

Today I’m sharing my version of that original recipe. It’s a wonderful way to prepare fish, and it has been one of my favourites since I was a child.

If your kids can be fussy about eating fish, this is worth trying. I often find that olives and capers can turn a simple dish into something they enjoy. Buon appetito!

Key Ingredients for Mahi Mahi Recipe

Mahi Mahi

Its mild flavour suits the sweet–sour caponata and keeps the dish balanced. Look for fillets with a fresh scent and flesh that looks moist and firm to the touch.

Green Olives

Bring gentle saltiness and depth to the sauce. Their savoury bite rounds out the vinegar and tomato concentrate. Choose pitted olives, so they slice neatly and cook evenly in the pan.

Capers

Add a sharp, tangy note that cuts through the richness of the tomato base. Rinsing them under cold water removes excess brine and keeps the seasoning balanced.

Vinegar

Provides the classic sweet–sour balance found in Sicilian dishes. It brightens the tomato concentrate and rounds out the sauce.

Find the complete list with measurements in the recipe card below.

How to Make Mahi Mahi with Caponata Sauce

Mahi Mahi

Step 1: Put the bay leaf, peppercorns, a slice of onion, and salt in a pot.

Step 2: Fill the pot with water and add the Mahi Mahi.

Step 3: Set the pot over medium heat and cook uncovered until the water starts boiling. Reduce the heat and keep simmering until the fish is fully cooked through.

Step 4: Drain the fish and let it cool down. Clean it and set it aside.

Caponata Sauce

Step 1: Blanch the chopped celery in salted boiling water.

Step 2: Chop the onion, place it in a frying pan, add ½ glass of water, and cook until the water evaporates.

Step 3: Add 3 tablespoons of extra virgin olive oil and sauté the onion for 1 or 2 minutes. Add the tomato concentrate, capers, olives, and the blanched celery. Pour in a little of the reserved celery cooking water and cook the sauce for 5 minutes.

Step 4: Dissolve the sugar in the vinegar and stir it into the sauce.

Step 5: Cook the sauce for a few minutes over medium-high heat, then turn the heat off and let it cool down.

Step 6: Cover the cooked Mahi Mahi with the cooled sauce. Serve at room temperature.

Extra Help from the Kitchen

Check Fillet Thickness – Select Mahi Mahi pieces with similar thickness to keep poaching even and prevent overcooking on thinner edges.

Dry the Celery Briefly – Drain the blanched celery well before adding it to the pan so the sauce keeps a steady consistency.

Taste Once Cooled – Adjust vinegar or sugar only after the sauce cools, as the sweet–sour balance settles during resting.

Let the Dish Rest – Leave the fish and sauce together for a short time before serving to help the flavours settle without softening the fish.

Variations and Twists

Bake the Fish with the Sauce – Place the Mahi Mahi in a small baking dish, spoon some of the tomato, olive, and caper mixture over the top, and bake until the fish turns opaque. This gives the dish a slightly richer finish and a softer texture on the fish.

Pan-Sear Before Adding the Sauce – Lightly dust the fish with flour and pan-sear it until golden on both sides, then spoon the cooled caponata over it. Searing adds a gentle crust that contrasts well with the soft sauce.

Swap Celery for Thinly Sliced Fennel – Use fennel instead of celery for a sweeter, more aromatic base. It softens quickly and blends well with olives, capers, and tomato concentrate.

Add a Splash of White Wine to the Sauce – Deglaze the pan with a small amount of dry white wine after the onions cook down. Let it reduce before adding the tomato concentrate to create a deeper, more rounded sauce.

Use Cherry Tomatoes for a Fresher Base – Replace the tomato concentrate with chopped cherry tomatoes and cook them down with the onions, olives, and capers. This gives the dish a lighter feel and a more delicate sweetness.

Storage and Shelf Life

Store the fish and caponata together in an airtight container in the fridge for 3–4 days. Bring it to room temperature before serving, as this dish is not meant to be reheated.

Freezing is possible, but the fish becomes softer once thawed, and the vegetables lose their bite, so quality may decline.

If you choose to freeze it, thaw it in the fridge and serve it cold without warming, as heating changes both texture and flavour.

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Mahi Mahi with Caponata Sauce Recipe

Light fish, bold vegetables, and a sweet–tangy caponata come together in this Mahi Mahi with Caponata Sauce, bringing a sunny, Mediterranean feel to your table.

Course: Main

Cuisine: Italian

Prep Time: 30 minutes

Cook Time: 30 minutes

Total Time: 1 hour

Servings: 3 to 4

Author: Manuela Zangara

Ingredients

Mahi Mahi

• 500 g – 1.1 lbs Mahi Mahi – cleaned
• 1 slice onion
• 1 tbsp parsley
• 2 – 3 bay leaves
• ½ tsp peppercorns
• salt
• water

Caponata Sauce

• ½ onion – chopped
• 2 ½ tbsp celery – chopped
• 10 green olives – pitted
• 1 ½ tbsp capers – rinsed
• 300 ml – 10 oz tomato concentrate
• 3 tbsp vinegar
• ½ tbsp sugar
• 2 tbsp extra virgin olive oil

Instructions

Mahi Mahi

1. Put the bay leaf, peppercorns, a slice of onion, and salt in a pot.
2. Fill the pot with water and add the Mahi Mahi.
3. Set the pot over medium heat and cook uncovered until the water starts boiling. Reduce the heat and keep simmering until the fish is fully cooked through.
4. Drain the fish and let it cool down. Clean it and set it aside.

Caponata Sauce

1. Blanch the chopped celery in salted boiling water.
2. Chop the onion, place it in a frying pan, add ½ glass of water, and cook until the water evaporates.
3. Add 3 tablespoons of extra virgin olive oil and sauté the onion for 1 or 2 minutes. Add the tomato concentrate, capers, olives, and the blanched celery. Pour in a little of the reserved celery cooking water and cook the sauce for 5 minutes.
4. Dissolve the sugar in the vinegar and stir it into the sauce.
5. Cook the sauce for a few minutes over medium-high heat, then turn the heat off and let it cool down.
6. Cover the cooked Mahi Mahi with the cooled sauce. Serve at room temperature.