BBQ Barramundi Burger with Grilled Cos

The first time I grilled lettuce for a burger, my neighbour looked over the fence like I had completely lost my mind. Five minutes later, after sneaking a bite of that smoky, charred cos, she asked for the recipe. That is exactly how this barramundi burger wins people over.

Last summer, I made these for a Sunday barbecue and watched my usually picky father-in-law go back for seconds. The combination of that zesty, slightly spicy tartare against the sweet, mild fish just works. Now it is requested at every family gathering.

Ingredients

• 4 x 150 g barramundi fillets: Barramundi is perfect for grilling because it is firm enough to hold its shape but still incredibly moist. Skinless makes assembly so much easier.
• 2 tbsp olive oil: Use a neutral oil with a decent smoke point since we are grilling at medium-high heat.
• Zest of 1 lemon: The essential oils in the zest give brightness without making the fish too acidic, which is key for balancing the rich flavours.
• 1 garlic clove, minced: One clove is enough to add depth without overpowering the delicate fish.
• 1 tsp sea salt: Sea salt adheres better to the fish and provides a cleaner, brighter seasoning than table salt.
• ½ tsp freshly ground black pepper: Freshly cracked pepper makes a noticeable difference in complexity and aroma.
• 4 brioche or burger buns: Brioche adds a touch of sweetness that complements the tangy tartare and mild fish perfectly.
• 1 large head cos lettuce: Cos (romaine) has enough structure to withstand grilling without disintegrating like softer lettuces would.
• 1 lemon, halved: Grilling the lemon caramelises its natural sugars and mellows the acidity, creating a deeper, more complex flavour.
• 2 jalapeños, halved and seeded: Grilling transforms jalapeños from sharp and biting to smoky and slightly sweet.
• ½ cup good-quality mayonnaise: This is the base of your tartare, so use a mayo you actually enjoy eating on its own.
• 2 tbsp finely chopped capers: Capers add those salty, briny pops of flavour that cut through the rich mayonnaise.
• 1 tbsp finely chopped dill: Dill pairs beautifully with fish and adds a fresh, herbal note to the tartare.
• 1 tbsp finely chopped parsley: Parsley adds colour and freshness without competing with the dill.
• 1 small shallot, finely diced: Shallots are milder than onions and provide just enough bite in the background.
• 1 tsp Dijon mustard: Dijon adds emulsification and a sharp, tangy edge that ties everything together.
• 8 thin slices ripe tomato: Ripe tomatoes provide acidity and juice that balance the creamy elements.
• 8 thin cucumber slices: Cucumber adds a cool, refreshing crunch and another layer of texture.

Instructions

Preheat the grill:

Get your BBQ or grill pan to medium-high heat. You want it hot enough to create nice char marks but not so aggressive that everything burns before cooking through.

Marinate the barramundi:

Whisk together the olive oil, lemon zest, garlic, salt, and pepper in a shallow dish. Coat the fillets thoroughly and let them sit for about 10 minutes while you prep everything else.

Prep the cos lettuce:

Separate the lettuce into large, sturdy leaves and brush them very lightly with olive oil. This helps them char rather than just wilt on the grill.

Grill the aromatics:

Place lemon halves cut-side down and jalapeños on the grill. Let them cook for 3-4 minutes until they develop nice char marks and soften. Remove them, let them cool briefly, then finely chop those jalapeños. Squeeze out about 2 tablespoons of juice from the grilled lemons.

Make the tartare:

In a bowl, combine the mayonnaise, those smoky chopped jalapeños, the grilled lemon juice, capers, dill, parsley, shallot, Dijon mustard, and salt and pepper to taste. Give it a good stir and pop it in the fridge to chill until serving time.

Grill the barramundi:

Cook those marinated fillets for about 3-4 minutes per side. You are looking for just opaque flesh and light char. Do not overcook it, as the fish will continue resting off the heat.

Char the lettuce:

Grill the cos leaves for just 1-2 minutes per side. They should be slightly wilted with visible grill marks and a gorgeous smoky aroma.

Toast the buns:

A quick toast on the grill, cut-side down, adds structure and prevents soggy burgers. Just 30-60 seconds should do it.

Assemble the burgers:

Spread a generous layer of that grilled lemon jalapeño tartare on both bun halves. Stack it up with grilled cos lettuce on the bottom, followed by the barramundi fillet, tomato slices, and cucumber. Crown with the top bun.

Serve immediately:

These are best enjoyed right away while the fish is still warm and the lettuce retains that perfect smoky crunch.

Save

There is something almost magical about watching sceptics take their first bite and immediately get it. The smoky charred lettuce, the bright zesty tartare, the perfectly flaky fish. It becomes the dish everyone talks about long after the plates are cleared.

Choosing the Right Fish

Barramundi is ideal because it is naturally buttery and firm enough for grilling, but snapper or cod work beautifully too. Just avoid delicate fish like sole or flounder, as they will fall apart on the grill. You want something that can hold its own against high heat and flipping.

Mastering the Grilled Lettuce

The trick is not to overthink it. Light oil, high heat, short time. You want the leaves to soften slightly and pick up char without turning into mush. If they are wilting too fast, move them to a cooler part of the grill or reduce the heat slightly.

Balancing Heat and Brightness

The grilled jalapeños lose some of their raw bite but gain a wonderful smoky depth. If you want more kick, leave a few seeds in or add a dash of hot sauce to the finished tartare. Taste as you go and adjust the lemon juice to hit your perfect balance of creamy, tangy, and spicy.

• Let the fish rest for a couple of minutes after grilling so it retains those precious juices when you bite in
• Toast your buns just before assembling so they stay crisp and structurally sound
• Have everything prepped and ready before the fish hits the grill because it cooks faster than you think

Save

This is the kind of meal that makes summer feel like summer. Smoky, fresh, zesty, and completely satisfying.

Recipe FAQs

→ What fish works best for these burgers?

Barramundi is ideal due to its firm texture and mild flavor, but you can substitute snapper, cod, or any other firm white fish fillet that holds up well on the grill.

→ Can I adjust the heat level?

Absolutely. Leave jalapeño seeds in for extra spice, or reduce the amount of grilled jalapeños in the tartare for a milder version. You can also add hot sauce to the condiment.

→ What makes grilled lettuce special?

Grilling cos lettuce briefly adds a delicious smoky flavor and slight wilt while maintaining crunch, creating a perfect texture contrast against the flaky fish.

→ How long does the tartare sauce keep?

The grilled lemon jalapeño tartare will keep refrigerated in an airtight container for up to 3 days, making it great for meal prep or leftover fish sandwiches.

→ What drinks pair well?

A crisp Australian Sauvignon Blanc cuts through the rich tartare beautifully, or try a pale ale for a refreshing beer option that complements the BBQ flavors.