Put a heavy-based frying pan over a medium-high heat. Brush the steaks and onions with 1 tbsp oil and season the steaks. Lay the steaks in the pan, pressing them flat with a palette knife, and fit the onions around them. Cook the steaks for 21⁄2-3 minutes on each side for medium rare, turning the onions when you turn the steaks.
Meanwhile, tip the wheat into a large saucepan. Add 4 tbsp water and stir. Heat through for 3-4 minutes, stirring once or twice.
Whisk together the 3 tbsp olive oil, vinegar and mustard to make a dressing. Crumble the feta into a bowl, add the tomatoes and rocket, then tip in the wheat. Pour in the dressing and mix. Serve with the steaks and onions.