Put the steaks in a dish and pierce a few times with a fork (this helps to tenderise them). Rub the Thai red curry paste into the steaks to cover them. Set aside to marinate while you make the salad.
Put a pan of water on to boil. Trim the French beans and slice them in half. Set aside.
Peel and finely slice the red onion and pop it in a bowl. Scrub the carrot and use a vegetable peeler to peel ribbons off it, peeling down each side till you get to the core. Finely slice the core. Add the carrot to the bowl. Halve the cherry tomatoes and add them to the bowl.
The water should be boiling now, so add the French beans and simmer for 2 mins. Drain, rinse under cold water to cool them down, then shake them try and tip them into the bowl.
Pick any thick stalks out of the watercress and add the tender leaves and sprigs to the bowl. Toss everything to mix. Peel and finely slice the onion. Set to one side.
Put a frying pan on a high heat for 2-3 mins till it’s smoking hot. Add ½ tbsp oil and the steaks. Fry for 3-5 mins on each side (depending on how well done you like your steaks). Lift them out of the pan and set them on a plate. Loosely cover with foil and leave to rest for 5-10 mins.
Add the onion to the frying pan and turn the heat down to medium. Season with a pinch of salt and pepper. Fry for 5-8 mins, stirring once or twice, till the onion is golden.
While the onion fries, halve the chilli, scoop out the seeds and white pith and finely chop the chilli. Pop it in a small bowl. Squeeze in the juice from the lime. Add ½ tbsp oil and a pinch of salt. Whisk together to make a dressing. Add to the bowl of veg and toss to mix.
Arrange the salad on 2 warm plates. Slice the steak and arrange on top. Spoon over the golden onion and serve.