Grilled Mackerel with Caramelized Onion and Lemon
Prep
20 mins
Cook
25 mins
Servings
4
Difficulty
Easy
This is one of my favorite weeknight dinners because it comes together in under an hour and tastes like you've spent all day cooking. Mackerel is incredibly affordable and packed with omega 3 fatty acids that are wonderful for your heart and brain. The caramelized onions add this beautiful sweet depth that perfectly complements the richness of the fish, while fresh lemon brightens everything up. It's simple enough for a busy Tuesday but elegant enough to serve to guests.
Ella x
Ingredients
- 4fresh mackerel fillets(skin-on, about 180g each)
- 3large yellow onions(thinly sliced)
- 5 tablespoonsolive oil
- 3garlic cloves(minced)
- 4fresh thyme sprigs
- 2lemon(1 for juice, 1 for slices)
- 1 teaspoonsea salt
- ½ teaspoonblack pepper
- 1 tablespoonbalsamic vinegar
- 2 tablespoonsfresh parsley(chopped)
Detail level
Instructions
- 1
Begin caramelizing the onions by heating 3 tablespoons of olive oil in a large skillet over medium heat. Add the sliced onions and a pinch of salt, stirring occasionally for 15-18 minutes until they turn golden brown and sweet.
Tip: Don't rush this step; low heat creates better caramelization and deeper flavor.
- 2
While onions cook, pat the mackerel fillets dry with paper towels and season both sides generously with sea salt and black pepper.
Tip: Dry fish grills better and develops a crispier skin.
- 3
Preheat your grill to medium-high heat and lightly oil the grates to prevent sticking.
Tip: If using a grill pan, heat it on the stovetop until just smoking.
- 4
Once onions are caramelized, stir in the minced garlic and balsamic vinegar, cooking for another minute until fragrant. Remove from heat and set aside.
Tip: The acidity of the vinegar balances the sweetness of the onions perfectly.
- 5
Place mackerel fillets skin-side down on the hot grill and cook for 5-6 minutes without moving them, allowing the skin to crisp.
Tip: Resist the urge to flip early; this creates a beautiful crust.
- 6
Carefully flip the fillets and grill for another 3-4 minutes until the flesh is opaque and cooked through. Place a lemon slice and thyme sprig on top of each fillet during the last minute.
Tip: The fish is done when it flakes easily with a fork and the internal temperature reaches 63°C.
- 7
Transfer grilled mackerel to serving plates and generously top each fillet with the caramelized onion mixture.
Tip: Keep the warm onions on top to maintain the mackerel's heat.
- 8
Drizzle with the remaining 2 tablespoons of olive oil and fresh lemon juice, then garnish with chopped parsley and additional thyme. Serve immediately.
Tip: The bright lemon juice cuts through the richness of both the fish and onions beautifully.
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