Ethné de Vienne’s Roasted Fish Fillets with Portuguese Spices and Onion Sofrito

Ingredients

• • 1 large Spanish onion, sliced into half-moons
  • ½ cup (125 ml) olive oil
  • 1 lb (450 g) delicate white fish fillets (such as sole, turbot, cod), rinsed and patted very dry
  • 3 tbsp Portuguese spice mix, ground
  • 6 tbsp butter
  • 1 tsp salt
  • 1 tbsp dukkah spice mix (optional)
  • 3 tbsp pistachios or almonds
  • Lemon wedges, for serving