Spicy rice burritos

Name: Spicy rice burritos
Ingredients: 1 tbsp rapeseed oil plus 2 tsp; 2 onions (320g) finely chopped; 150g brown basmati rice; 2-3 tsp mild chilli powder; 1 tsp each ground coriander and cumin; 400g can chopped tomatoes; 2 tbsp tomato purée; 400g can black beans drained; 180g spelt wholemeal flour plus extra for dusting and a little for sprinkling; 2 avocados; 1 lime juiced; 4 large iceberg lettuce leaves (about 120g); 198g can sweetcorn drained; 120g pot bio yogurt; 15g coriander finely chopped; 12 Kalamata olives halved