Equipment
Ingredients
Aromatics and Produce
- 30 ml extra-virgin olive oil
- 1 yellow onion, peeled and finely diced
- 2 green bell pepper, stemmed, seeded, and diced into 1 cm pieces
- 3 garlic, peeled and thinly sliced
- 500 g roma tomato, stemmed, cored, and coarsely chopped
Seasoning and Finish
- 15 ml sherry vinegar
- 2 g fresh thyme, leaves stripped from stems
- 4 g fine sea salt
- 1 g black pepper, freshly cracked
- 10 g flat-leaf parsley, finely chopped
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 131 kcal
- Protein
- 2 g
- Carbohydrates
- 14 g
- Fat
- 8 g
- Fiber
- 6 g
- Sodium
- 401 mg
- Saturated Fat
- 1 g
- Trans Fat
- 0 g
- Potassium
- 489 mg
- Calcium
- 49 mg
- Iron
- 1.5 mg
- Magnesium
- 10 mg
- Phosphorus
- 20 mg
- Zinc
- 0.2 mg
- Vitamin A
- 188 mcg
- Vitamin C
- 90 mg
- Water
- 65 g
Sources: Aggregated Public Data, USDA FoodData Central
Method
Place the yellow onion, green bell peppers, garlic cloves, and roma tomatoes on the cutting board. Using a chef knife, peel and finely dice the onion, core and dice the green peppers into 1 cm squares, peel and thinly slice the garlic, and coarsely chop the tomatoes.
Place the large skillet with lid on the stovetop over medium heat at 175°C (350°F) and pour in 30 ml of extra-virgin olive oil measured with the liquid measuring cup.
Add the diced yellow onion and diced green bell peppers to the skillet and sauté over medium heat for 6 minutes, stirring frequently with the wooden spoon.
Add the sliced garlic to the skillet and sauté for 1 minute while stirring continuously with the wooden spoon.
Add the chopped roma tomatoes, 15 ml sherry vinegar, 2 g fresh thyme leaves, 4 g fine sea salt, and 1 g freshly cracked black pepper weighed on the digital kitchen scale into the skillet, stirring with the wooden spoon to combine and release pan drippings.
Cover the skillet with the lid, lower the heat to maintain a gentle simmer at 95°C (203°F), and cook undisturbed for 15 minutes.
Remove the lid from the skillet and simmer uncovered over medium-low heat at 100°C (212°F) for 5 minutes, stirring occasionally with the wooden spoon until excess surface moisture evaporates.
Remove the skillet from the heat source and fold the 10 g of chopped flat-leaf parsley into the warm sauce using the wooden spoon.
Spoon 150 g of the warm sauce over prepared fish steaks, verifying with an instant-read food thermometer that the fish has reached a minimum safe internal temperature of 63°C (145°F) with opaque flesh that separates cleanly along the flake.
Chef's Notes
- Green bell peppers provide an herbal, slightly bitter counterbalance that pairs exceptionally well with fatty or dense fish steaks like swordfish, halibut, tuna, or salmon.
- Cooking the peppers gently in olive oil tenderizes their skins and coaxes out natural sugars, rounding out sharp green notes without turning the vegetables to mush.
- A modest splash of sherry vinegar heightens the natural acidity of fresh tomatoes and cuts right through rich fish oils without overwhelming delicate seafood flavors.
- Always check fish steak doneness using an instant-read food thermometer placed in the thickest section, ensuring an internal temperature of at least 63°C (145°F) before topping with the warm sauce.
Storage
Refrigerator: 4 days — Cool leftovers to room temperature within two hours and store in an airtight glass container.
Freezer: 3 months — Transfer cooled sauce to freezer-safe containers, leaving 1 cm headspace for expansion.
Reheating: Reheat in a saucepan over medium-low heat until bubbling rapidly throughout and registering at least 74°C (165°F) on a food thermometer.
Troubleshooting
Sauce is overly watery and fails to coat fish steaks cleanly
Cause: The fresh tomatoes released excessive water, or the sauce was not reduced sufficiently with the lid off
Fix: Return the skillet to medium heat and simmer uncovered for an extra 4 to 6 minutes, stirring frequently until thickened
Prevention: Ensure the lid is fully removed during the final reduction step to promote evaporation
Green bell peppers taste unpleasantly crunchy or astringent
Cause: The peppers were not sautéed long enough before introducing acidic tomatoes and vinegar
Fix: Cover the skillet tightly and simmer on low heat for an additional 10 minutes to soften the vegetable fibers
Prevention: Sweat peppers and onions in olive oil until fully pliable before adding acid, which halts pectin softening
Garlic or vegetables develop scorched black flecks with a bitter taste
Cause: Pan temperature was too high or garlic sat against the dry bottom without stirring
Fix: Cannot be fixed if burnt particles are stirred throughout the sauce; discard and restart the aromatic base
Prevention: Keep heat moderate when introducing garlic and stir constantly for no more than 60 seconds
Cultural Context
Originating in the sun-drenched coastal traditions of the Mediterranean basin, sauces combining sweet nightshades and olive oil like Basque piperade and Italian peperonata have long been staples of seaside cooking. Fishermen historically paired stewed garden peppers and sun-ripened tomatoes with thick-cut catches of the day to add moisture, acidity, and vibrant color to simply grilled fish steaks.
