Combine marinade ingredients in a bowl and stir to combine.
Place salmon in shallow bowl or zip-top bag and pour marinade over fish, turning pieces to coat. Put salmon in fridge and marinate for at least 2 hours.
Combine quinoa, coconut milk and water in small saucepan and bring to a boil. Reduce to low, stir, cover and simmer until liquid is gone and quinoa is fluffy, about 15 minutes.
Meanwhile, steam or saute peas over medium heat for 5 minutes. Run peas under cold water, drain and set aside.
Heat a 12-inch cast-iron pan over high heat for 3 minutes. Add oil and swirl to coat. Wait 1 more minute, until oil shimmers, and add salmon, skin-side down. Take care not to move fish after you place it on the pan. Reduce heat to medium-high and cook until skin is browned, about 4 minutes. Flip fish flesh-side down, and cook 3-4 more minutes, until salmon is opaque. Remove fish from pan and set aside.
In a medium bowl, toss peas with butter and lemon juice and finish with a pinch of flake salt.
To serve, spoon quinoa into large bowls or onto plates and place the salmon on top. Serve peas on the side. Green onions or sesame seeds also make great garnish.