Set your oven to 100°C/Fan 80°C/Gas 1. Unwrap the tortillas and place them in a large square of foil. Loosely wrap them foil around them to create a parcel, then pop it in the oven. The tortillas will warm will you make the taco fillings. No foil? See our tip on other ways to warm the tortillas.
Pull the silks and leaves off the sweetcorn cob. Cut a small slice off the thick end of the corncob, so it stands upright on your chopping board, and run your knife down it to slice off the sweetcorn kernels. Pop a deep frying pan or wok on a medium heat and add ½ tbsp oil and the sweetcorn kernels. Fry, stirring every so often, for 3 mins till the kernels are browned and a little charred (be careful – if the pan is too hot the kernels will try to jump out).
While the sweetcorn kernels fry, peel and finely chop the red onion. Tip the browned sweetcorn kernels out of the pan into a bowl and add another ½ tbsp oil to the pan. Add the onion with a pinch of salt and fry, stirring often, for 5 mins till the onion is glossy but hasn’t picked up too much colour. If it starts to brown, add a splash of water.
While the onion fries, halve the chilli and scrape out the seeds and white membrane (or leave them in if you prefer a spicier dish). Finely chop the chilli. Trim the dry ends off the chard stalks, then finely chop the chard stalks and leaves.
Stir the chilli, chard stalks and leaves into the onion. Fry, stirring often, for 2-3 mins till the chard is wilted and the stalks have lost their crunch. Add 1 tbsp tamari to the pan and stir to mix. Taste and add more tamari, if you think it needs it.
Divide the warm tortillas between 2 plates. Top with the wilted chard and toasted corn kernels, and crumble over half the pack of feta. Serve straight away.