Watermelon tuna is an easy fish substitute that tastes like the real deal! Marinate cubed watermelon in a blend of seasonings to mimic the flavor of ahi tuna steak, then add it to poke bowls, sushi, and more.
It may sound strange, but with a few simple ingredients and a little bit of patience, you can transform watermelon into ahi tuna.
Okay, not literally. But you’ll be surprised how close this watermelon tuna comes to the taste of real tuna. Just like my vegan fish sticks and vegan fish tacos, it’s all about the seasonings you add—watermelon naturally looks like raw tuna, but to get it to taste like it too, we add nori for that fishy flavour. The rest of the marinade ingredients have the same flavours of the marinade used to prepare tuna for poke, which makes for a convincing plant-based tuna to use in meal bowls and sushi rolls.
Friends, you are going to flip for this recipe. Although it takes some time for the marinade to soak in and do its work, everything else about this watermelon tuna is a cinch. Just dice the watermelon, whisk the marinade, and your job is done! With the summer months approaching, this vegan tuna watermelon is perfect for hot days when you just don’t want to turn on the oven.
Notes on Ingredients
Scroll down to the recipe card to find the ingredient quantities and recipe instructions.
- Watermelon – This vegan tuna recipe is one of the rare occasions when you actually want a watermelon that’s a little bit under-ripe. The sweeter the melon, the less convincing your watermelon tuna will be as an ahi tuna substitute.
- Rice wine vinegar – Be sure to use the unseasoned variety, as it doesn’t have added sugar.
- Soy sauce – Use low-sodium soy sauce or tamari.
- Sesame oil
- Green onion
- Dried nori sheet – This is key to that seafood flavour. Don’t skip it!
- White sesame seeds
- Black sesame seeds
Is Toasted or Untoasted Nori Better?
You’ll be crumbling the nori sheet, so purchase toasted nori; it’s more brittle and thus easier to crumble. Untoasted nori will work too, but you may want to use a knife or kitchen shears to prepare it instead of trying to crumble it.
How to Make Watermelon Tuna
While this is quick to prepare, as I mentioned above, you will need to account for the time needed for the watermelon tuna to marinate, so it’s not the kind of thing you can make on a whim and enjoy for dinner a few minutes later. On the flip side, this vegan tuna is an amazing option for meal prep lunches and dinners!
- Make the marinade. Stir the rice wine vinegar, soy sauce, sesame oil, green onion, crushed nori sheet, and sesame seeds in a large bowl or airtight container.
- Add the watermelon. Place the watermelon in the bowl with the sauce and stir until everything is combined and the watermelon is evenly coated.
- Marinate. Cover the bowl and let the watermelon marinate in the refrigerator for at least 24 hours, but ideally 48 hours.
- Serve. Let the watermelon sit at room temperature for a few minutes and serve.
Tips for Success
This vegan watermelon tuna is a cinch to make, but these simple tips will help you make sure it turns out absolutely perfect.
- Buy a seedless watermelon. You don’t want crunchy black seeds in your vegan tuna! If you do use a regular watermelon, remove as many of the seeds as possible before marinating it.
- Submerge the watermelon in the marinade. If possible, completely submerge the watermelon; if not, you’ll at least want to ensure that the melon cubes are in an even layer so each piece is in the liquid and then flip the melon halfway through the chilling time.
- Be patient. You’ll really get the best results if you let the vegan watermelon tuna marinate for the full 48 hours.
How to Use Watermelon Tuna
I developed this watermelon tuna recipe to use in poke bowls, so the marinade gives it a similar flavor to tuna poke. But you don’t have to limit yourself to using it in poke! You can make a meal bowl with sushi rice, watermelon tuna, and cucumber slices, or make it into sushi rolls or vegan sashimi.
How to Store Leftovers
Any leftover watermelon tuna should be stored in an airtight container in the fridge for 3 to 4 days total (including the initial marinating time).
Can I Freeze This Recipe?
I don’t recommend freezing watermelon tuna, as the texture is likely to suffer with freezing and thawing.
More Watermelon Recipes
- Watermelon Mojitos
- 3-Ingredient Easy Watermelon Granita
- Watermelon Mint Popsicles (Three Ingredients)
- Watermelon Feta Salad with Balsamic Reduction
Enjoy friends! If you make this vegan watermelon tuna, please snap a photo and tag #jessicainthekitchen on Instagram! We’d also love it if you would leave a comment below, and give the recipe a rating! Thanks so much!
- 2 cups 1 inch cubed watermelon
- 2 ¼ tablespoons rice wine vinegar
- 3 ½ tablespoons soy sauce, low sodium
- 1 tablespoon sesame oil
- 2 stalks green onion, diced
- 1 sheet dried nori sheet , crushed
- ¼ teaspoon white sesame seeds
- ¼ teaspoon black sesame seeds
- In a bowl, add the rice wine vinegar, soy sauce, sesame oil, green onion, crushed nori sheet and the sesame seeds. Stir to combine. Add the cubed watermelon in and stir everything together to combine. Ensure that all the watermelon is marinated in/under the liquid.
- Cover and allow to marinate in the fridge for at least 24 hours, preferably up to 48 hours for the best texture.
- Remove from the fridge, and enjoy as desired! You can let it sit out a bit to come back closer to room temperature and serve in a poke bowl.
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