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Fish, Italy

Sweet and sour tuna with onions and potatoes

Sweet and sour tuna with onions and potatoes is a Sicilian dish for 4 people, ready in 45 minutes, rated easy, at about €4.20 per person. Its success depends on timing the vinegar, added at the end of cooking the onions so it caramelizes with the sugar instead of turning sharp, and on a short sear that keeps the tuna pink at the center.

I'm suggesting a Sicilian dish, pan seared tuna topped with onions melted in vinegar and sugar, a dish that splits the difference between sweet and sour.

Sweet and sour tuna with onions and potatoes
Total time
45 min
Difficulty
Easy
Cost per person
€4.20
Calories per person
540 kcalcalculated by Kiloach, your weight coach
Season
Summer

This dish plays on a clear contrast, the seared tuna stays firm and barely pink while the onions slowly melt before soaking up sugar and vinegar that turn them into a glossy, syrupy sauce. Fresh mint added at the very end cuts through the sweetness and wakes the whole plate back up. The potatoes give a neutral base that balances everything out.

It's a summer recipe that doesn't need constant attention, perfect for a weeknight when you want to step away from the usual tomato sauces, but just as fitting for a relaxed Sunday table with adults. Mon Chou likes dishes like this one that change things up with very few ingredients, a Sicilian classic that travels well to your plate.

The ingredients

4 people

Fish counter

  • Tuna steaks 4

Fruits and vegetables

  • Onions 4
  • Mint 8 leaves
  • Potatoes 800 g

Pantry

  • Wine vinegaroften in the pantry 8 tbsp
  • Sugaroften in the pantry 3 tbsp
  • Olive oiloften in the pantry 4 tbsp
  • Saltoften in the pantry 1 pinch
  • Pepperoften in the pantry 1 pinch

Allergens Fish

The step by step recipe

  1. Cook the potatoes in salted water. 20 min

    Start the potatoes in cold water and prick them, they'll stay firm.

  2. Thinly slice the onions and cook them in the oil over low heat until soft. 15 min

    Add a spoonful of water if the onions stick, they should melt without browning.

  3. Add the sugar, then the vinegar, and let it caramelize. 5 min

    It's ready when it turns syrupy and glossy, coating the back of the spoon.

  4. Sear the tuna steaks in a very hot pan. 4 min

    Sear the tuna 2 minutes per side, the center should stay pink.

  5. Top the tuna with the sweet and sour onions, scatter with mint, and serve with the potatoes.

    Add the mint at the very last moment, its freshness contrasts with the sweetness.

Our tips to get it right

  • Pick thick tuna steaks, at least 2cm, so they stay pink in the middle despite the hot sear.
  • Slice the onions into thin, even strips so they all melt at the same rate instead of some burning.
  • Make the sweet and sour onions ahead of time, they taste better once cooled and gently reheated before serving.

The variations

  • Swap the tuna for mackerel or sardine fillets, they pair just as well with the sweet and sour sauce.
  • For a fish free version, replace the tuna with grilled eggplant slices, they soak up the onion sauce nicely.
  • To save time, cut the potatoes into small cubes instead of cooking them whole, they'll be ready in 10 minutes.

What to serve it with

  • A glass of chilled dry white wine
  • A lemony arugula salad
  • Crusty country bread for the sauce

Storage

The sweet and sour onions keep for 2 to 3 days in the refrigerator in a sealed container and reheat gently in a pan. Cooked tuna doesn't keep as well, it's best to cook it right before serving. This dish doesn't freeze well, the tuna would lose its texture and the potatoes would turn mushy.

Questions about this dish

Can you use a different vinegar instead of wine vinegar?

Yes, cider vinegar or sherry vinegar both work well and add a slightly different note. Avoid strong vinegars like white vinegar, which can overpower the tuna.

Can you make the sweet and sour onions ahead of time?

Yes, it's actually recommended, they develop more flavor after resting for a few hours. Reheat them gently in a pan just before topping the tuna.

How do you know when the tuna is cooked enough?

Sear it for about 2 minutes per side in a very hot pan for a 2cm thick steak. The center should stay pink, otherwise the tuna dries out and loses its tenderness.

Can you swap the mint for a different herb?

Fresh basil is a good alternative, it keeps that fresh contrast against the sweet onions. Avoid dried herbs, they won't give the same effect.

How long does it take to make a sweet and sour tuna with onions and potatoes?

Count 45 min in total, prep and cooking included. The recipe is rated “easy”.

How many calories are in a sweet and sour tuna with onions and potatoes?

About 540 kcal per serving, for a recipe meant for 4 people. Calories are calculated by Kiloach, your weight coach, the app that partners with Mon Chou.

How much does a sweet and sour tuna with onions and potatoes cost?

About €4.20 per serving, or €16.80 for 4 people, based on average supermarket prices.

What allergens does this recipe contain?

This recipe contains fish. Always check the labels of the products you buy.

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