Make the salsa: In a medium-size bowl, combine all the ingredients and let sit at room temperature while you prepare the steak and corn.
Make the steak:Preheat the oven to 400°F (205°C). Let the steak sit out until it comes to roughly room temperature; this will help it cook more evenly. Season each side of the steak with ½teaspoon of the salt and a very generous amount of pepper.
In a large ovenproof frying pan, preferably cast iron, heat the grapeseed oil over high heat until very hot, about 3 minutes. Place the steak in the pan and cook until nicely browned, about 3 minutes. Flip and cook until the other side is browned as well, about 2 minutes.
Transfer the pan to the oven and cook for 5 minutes for medium-rare. Remove the steak to a carving board and let rest while you cook the corn.
Make the corn: In a wide heavy-bottomed sauté pan, heat the olive oil over medium-high heat for about 30 seconds. Add the scallions and cook until they are soft and some pieces are just beginning to brown, 2 to 3 minutes.
Add the corn kernels, salt, and pepper to taste. Cook, stirring often, until the corn is cooked through but not browned, about 4 minutes. Remove from the heat and stir in the lime zest.
Spread the corn on a platter. Cut the steak against the grain into pieces ½inch (12millimeters) thick. Arrange the steak over the corn. Spoon the salsa on top of the steak and serve.