Preheat oven to 205°C/400°F. Spread the frozen sweetcorn onto a foil-lined baking tray, season with Cajun seasoning, salt and pepper, and roast for 30 minutes, stirring halfway, until golden and slightly charred. Allow to cool completely.
While the corn roasts, make the dressing. Whisk together the Greek yogurt, finely chopped coriander, lime juice, salt and pepper in the base of a large bowl.
Add the cherry tomatoes, diced peppers, and two thirds of the crumbled feta to the bowl.
Pat the steaks dry with kitchen paper and season with salt and pepper. Heat a pan over high heat until smoking, add the olive oil, and sear the steaks for 1–2 minutes per side. Rest for 5 minutes, then slice thinly against the grain.
Add the cooled corn to the bowl and toss everything together until fully combined. Divide into 5 containers and top with sliced steak, reserved feta, a garnish of coriander, and a lime wedge. Store in the fridge for up to 4 days.