Raspberry butter against raw tuna sounds improbable until you taste the sauce. This is a tataki: tuna sits in soy sauce and citrus for an hour, gets seared for seconds on each side, then is sliced thin and dressed with a sauce built from the marinade and melted Bordier Raspberry Butter. The raspberry reads as acidity more than sweetness, which is exactly what soy sauce wants next to it. Plan on about fifteen minutes of actual work and an hour of waiting.
At a glance
- Difficulty: Medium
- Serves: 2
- Active time: About 15 minutes, plus at least 1 hour marinating
- Cook: Seconds per side. Bordier states no cooking time for this one
- Key ingredient: 50 g Bordier Raspberry Butter
Why this works
Bordier's Raspberry Butter dates to 2006 and came out of a conversation with a pastry chef friend. It is a salted butter carrying tangy raspberry, and the salt is what keeps it from behaving like a dessert. Set against soy sauce, the fruit lands closer to a vinegar reduction than to jam. That is the whole trick here: you are not sweetening tuna, you are giving it a fruit acid with a fat behind it.
The method is a classic tataki. Acid from the marinade firms the outside of the tuna slightly, the sear sets a thin cooked edge, and the center stays raw and cool. The sauce is built by melting the butter gently and then pouring the strained marinade into it, so the soy and citrus loosen the butter into something pourable rather than greasy. Every Bordier butter is churned by hand in Brittany on a traditional wooden malaxeur, which leaves it softer and quicker to melt than a hard industrial block. Handle it with that in mind.
Ingredients
Serves 2 as an appetizer. Buy the best tuna you can find, since most of it stays raw.
| Ingredient | Metric | US |
|---|---|---|
| Raw tuna | 200 g | 7 oz |
| Bordier Raspberry Butter | 50 g | 1.8 oz, about 3 1/2 tbsp |
| Lime | 1/2 | 1/2 |
| Light salty soy sauce | 6 tablespoons | 6 tbsp |
| Radish, pink or black | A few slices | A few slices |
| Sesame seeds | 1 teaspoon | 1 tsp |
| Oxalis sprouts (optional) | A few | A few |
Method
Step 1: Marinate the tuna and start the sauce
Put the tuna in a bowl. Pour over the soy sauce and the citrus juice, then strain the bowl. Chill for at least an hour. Lift the tuna out, and melt the Bordier Raspberry Butter gently in a pan, taking care not to let it brown. Pour the tuna marinade into the pan with the butter.
Step 2: Sear, slice, and sauce
Sauté the tuna in the butter just long enough to score each side, then take it out. Cut it into thin slices with a sharp knife. Lay a few slices on each plate and spoon the sauce over them.
Step 3: Garnish
Scatter over the sesame seeds, the radish slices, and the oxalis sprouts.
Tips from our kitchen
- Keep the butter blond. Raspberry butter carries fruit sugars as well as milk solids, so it colors and then scorches faster than plain butter. Melt it over low heat and pull the pan the moment it is liquid. Browned raspberry butter tastes bitter and the sauce cannot be rescued.
- The pan has to be hot, the fish has to be cold. Take the tuna straight from the marinade to a properly hot pan and count seconds, not minutes. If the fish is at room temperature the heat travels through it and you get a gray band instead of a clean raw center.
- Chill the tuna before slicing. A few minutes in the freezer after searing firms the block and lets a sharp knife cut clean sheets. A dull knife tears the fibers and the slices fall apart on the plate.
- Lime or lemon. Bordier's ingredient list calls for half a lime, but the method text says lemon juice. We follow the ingredient list and use lime, which sits better against the raspberry. Either will work if lime is what you cannot find.
- Do not add salt. The soy sauce is salty and the Bordier Raspberry Butter is a salted butter at 2.8% salt. Taste the sauce before you reach for anything else.
- Sauce at the last second. The sauce is a warm butter emulsion and it will split if you hold it. Build it, plate the tuna, pour, and serve.
How to serve it
Serve this cold or barely warm, as a first course with plain steamed rice or good bread and nothing else competing. A dry Riesling or a chilled Muscadet handles the soy and the fruit at the same time. If you like this style of cold seafood plate, our guide to La Brújula Spanish conservas covers a pantry version of the same idea, tinned fish dressed simply and eaten straight from the plate.
Where to buy Bordier Raspberry Butter in the US
The French Pantry ships Bordier butter across the United States in insulated overnight packaging, straight from the workshop in Brittany.
- Churned Seasonal Raspberry Butter by Bordier (4.4 oz): salted Breton butter worked with tangy raspberry, a seasonal flavor that comes and goes.
For the rest of the range, including the unsalted and demi-sel blocks, browse the Maison Bordier collection.
Frequently asked questions
How much Bordier Raspberry Butter do I need for this recipe?
The recipe calls for 50 g. Bordier blocks are 4.4 oz, or 125 g, so a single block covers this twice over with plenty to spare for toast.
Can I use a different Bordier butter?
The Salted butter is the closest structural match and will give you a clean beurre blanc style sauce, but you lose the fruit acidity that makes the dish work. If you want to stay close to the original, wait for the raspberry to come back into season rather than swapping it out.
What kind of tuna should I buy?
Buy a center-cut loin piece from a fishmonger you trust and tell them it is being served rare. Most of this tuna stays raw, so quality and freshness matter more than the cut.
How should I store the butter?
Keep it in the refrigerator in its wrapper or an airtight box, away from anything strongly scented, since butter takes on odors readily. Bring only the piece you need up to cool room temperature before melting.
Does Bordier butter need refrigeration?
Yes. Bordier butter is a fresh, hand-churned product and ships cold. Refrigerate it as soon as it arrives.
Can I marinate the tuna longer than an hour?
Bordier says at least an hour and does not give an upper limit. In our kitchen we stop at about three hours, after which the soy starts to cure the outside of the fish and the texture turns firm rather than silky. That guidance is ours, not Bordier's.
Related reading
- Bordier Butter: What It Is, Why Chefs Love It, and How to Use It
- How to Choose Your French Butter: A Buyer's Guide
- Terre Exotique
Recipe and photograph adapted from Maison Bordier, with thanks. The French Pantry is an authorized US retailer of Bordier butter.