In a small blender place the roughly chopped half onion and tomato, and garlic cloves.Blitz until coarsely chopped.
In a medium saucepan heat half of the oil over medium heat.Add onion mixture and cook, stirring, for 2 minutes until fragrant. Add rice and cook, stirring, for 30 seconds to 1 minute until slightly browned and the liquid absorbs. Add the stock, stir, and increase heat to bring to a boil. Cover, reduce heat to low and simmer for 8-12 minutes, until liquid is absorbed. Keep covered and remove from heat to rest.
While rice is cooking, in a small bowl combine remaining oil and juice of 1 lime to make dressing.
In a serving bowl combine radishes, cucumber, corn, beans, avocado and half of the coriander. Pour over dressing and toss well to coat.
In another bowl, gently combine capsicum, pineapple, chilli and mint with the remaining coriander and lime juice, the diced tomatoes and the finely chopped onion.
Divide rice among four plates.Top with black bean salad, pineapple salsa, a few tortilla chips, sour cream and chilli sauce, if using.