Preheat the oven to 250 degrees F.
Remove the fish from the refrigerator and let it come to room temperature, about 10 minutes.
Coat a large saute pan with olive oil and bring the pan to a high heat.
Pat the fish dry with paper towels and sprinkle both sides with salt.
When the oil is very hot but not smoking, gently add the fish to the pan. DO NOT try to move the fillets. After 2 to 3 minutes, shake the pan gently and the fish should unstick itself. If the pan was hot enough, it will release. If not, using a fish spatula, GENTLY scrape it from the bottom of the pan. Cook the fish for 1 more minute and then turn it over, placing it on a wire rack set in a sheet tray. Transfer to the oven and cook until cooked through, another 10 to 12 minutes.
Ditch the oil from the pan and add the orange juice, zest, chopped oranges, sugar, vinegar, thyme and a pinch of salt. Bring the liquid to a boil (BTB), reduce it to a simmer (RTS) and reduce the liquid by half. Taste and adjust the seasoning. The sauce should have a great tangy, sweet and sour mix.
Spoon the sauce over the seared cod and serve immediately.