Sweet Potato Toast with Sardines and Pickled Onion
The idea is this: you slice a sweet potato lengthwise into thick planks, run them through the air-fry setting on your oven until they're tender inside and slightly caramelized outside, and use those planks as the vehicle for a toast situation. Topped with tinned sardines, quick-pickled red onion, and a smear of good mustard, this is a whole meal on a sweet potato; high in omega-3s, rich in complex carbs, and more satisfying than it has any right to be. Sardines are one of the most nutrient-dense, sustainable fish you can eat, and they're great when paired with something sweet and acidic to balance their oiliness. If you've written off sardines in the past, we suspect this is the recipe that changes your mind.
- DF
- GF
- PRO
Calories ~370 · Protein ~25g · Carbs ~27g · Fat ~18g
Ingredients
For the pickled onion:
- 1 small red onion, very thinly sliced (about ¾ cup)
- ¼ cup (4 tablespoons) apple cider vinegar
- 2 tablespoons fresh lime juice
- 1 teaspoon honey
- Pinch of fine sea salt
For the sweet potato toast:
- 1 large sweet potato, scrubbed
- 1 tablespoon extra-virgin olive oil
- Fine sea salt and freshly ground black pepper
For assembly:
- 2 tins sardines in olive oil, drained
- 1 tablespoon whole-grain Dijon mustard
- 1 tablespoon capers, drained
- Fresh parsley or chives, roughly chopped
- Flaky sea salt
Method
- Make the pickled onion first so it has time to mellow: Combine the sliced onion, apple cider vinegar, lime juice, honey, and salt in a small bowl. Toss well and press the onions down into the liquid. Toss again at the 10-minute mark to ensure all onion slices contact the brine. In 15–20 minutes, the onions will turn bright pink and soften into something tangy and sweet.
- Slice the sweet potato lengthwise into ½-inch-thick planks. You should get 4–5 planks depending on the width of the potato. Brush both sides of each plank with olive oil and season with salt and pepper.
- Preheat your oven to 400°F (200°C) on the air-fry setting. Place the sweet potato planks directly on the oven rack (or on a wire rack set inside a sheet pan for easier handling). Air-fry for 18–22 minutes, flipping once halfway through, until the planks are golden at the edges, tender when pierced with a fork, and lightly caramelized on the surface. If you own a standalone air fryer, cook at 400°F for 15–20 minutes, flipping once, until tender when pierced with a fork.
- While the sweet potato cooks, drain the sardines and gently separate them into 2–3 rough pieces per fillet with a fork. You want visible chunks, not a paste.
- Assemble immediately when the planks come out: Spread a thin layer of Dijon mustard on each plank. Top with sardine pieces, a pinch of capers, and a small pile of the drained pickled onion. Scatter fresh herbs over the top and finish with flaky sea salt.
To serve: Eat while the sweet potato is still warm; the contrast between hot-sweet potato and cool pickled onion is the whole point.
Variations & Notes
- Extra Hungry: Add a soft-boiled or jammy egg (7 minutes in boiling water, then ice bath) halved on top. Serve two planks per person with a simple green salad alongside.
- Substitutions: Smoked trout or tinned mackerel works in place of sardines. Good-quality tinned tuna in olive oil is a milder, more crowd-pleasing alternative. Lemon juice can replace lime juice in the pickle. The pickled onion recipe makes more than you need: keep the rest in the fridge for up to 10 days and use it on everything.
- Storage: The pickled onion keeps refrigerated for up to 10 days. The sweet potato planks are best eaten right away but can be reheated on the air-fry setting at 375°F for 5 minutes. Assemble to order.