Steak onion fajitas with sweetcorn salsa

Name: Steak & onion fajitas with sweetcorn salsa
Ingredients: 1 very ripe avocado; 2 limes, 1 juiced, 1 cut into wedges; 100g sweetcorn from a can, or frozen and defrosted; 1 tomato, deseeded and finely chopped; ½ a small bunch coriander, chopped; 1 tsp garlic-infused olive oil; 2 red onions, cut into wedges; 140g lean beef steak, sliced and all fat removed; 1 tbsp fajita seasoning; 4 small wholemeal flour tortillas; shredded iceberg lettuce and sliced jalapeño peppers, to serve