Zest the lime and the lemon. Cut the zest into julienne and blanch them for a few seconds and cool them in ice water. Cut a slice of a lemon and set it aside. Squeeze the juice from the lemons.
Melt the chopped onion over medium heat in a large pan and add the fish and lemon juice just before the onion begins to brown. Season. Cook further for +/- 5 minutes or just until the fish begins to fall apart. Add the garlic and hot pepper flakes, taste and adjust if necessary, continue cooking for one minute.
Reheat the linguine in lightly salted boiling water for 75 seconds and drain. Pour them into the pan with the fish and sauce and mix gently. Add one or two teaspoons of pasta cooking water if you don't have enough sauce.
Arrange on warm plates with the linguine at the bottom and fish and sauce on top. Garnish with the lemon zest, chopped chives and some chili flakes.
Tip: to make a takeaway dish, it is best to steam the fish and to make a lemon sauce with some butter and cream. And then dress everything in the cold line.