In a small bowl, mix together the scallions, cilantro, jalapeño, garlic, lime zest, lime juice, honey, olive oil, salt and pepper. Taste for seasoning and adjust as needed, then set aside while you prepare the fish.
Pat the barramundi fillets very dry, then season both sides with salt and pepper. Heat the oil in a large heavy bottomed sauté pan (cast iron works great) over medium high heat. Dredge each fillet lightly in flour, tapping off any excess, and place in the pan skin-side down. Use a fish spatula to press down on the fillet for about 30 seconds to prevent the skin from curling up and help it cook evenly.
Cook until opaque around the edges, then flip to finish on the other side. It should take about 2-3 minutes on each side, depending on thickness. Repeat with the remaining fillets.
Transfer the fish to a platter and spoon sauce over top. Serve immediately with warm tortillas and extra sauce on the side.