Taco salad

Name: Taco salad
Prep time: 20 min
Cook time: 30 min
Total time: 50 min
Cuisine: American, Mexican, Latin American
Ingredients: 1 red onion, sliced; 1 lime, juiced; 1 tbsp sunflower oil; 400g lean beef mince; ½ pack taco or fajita seasoning; 1 tbsp tomato purée; 400g can black beans, drained but not rinsed; 200g tortilla chips; 1 small iceberg lettuce, shredded; 2 avocados, peeled and sliced; 2 tomatoes, chopped into chunks; 100g feta, crumbled; small bunch of coriander, chopped or leaves picked; ½ lime, juiced; 5 tbsp soured cream; chilli sauce (optional), plus extra to serve