Rinse the rice under cold water and tip into a small pan. Pour in 150ml boiling water and add a pinch of salt. Cover, bring to the boil and then turn the heat right down so the rice gently simmers for 25 mins till all the water has been absorbed. Then take the rice off the heat and let it sit in the pan for 5 mins, with the lid on, to steam the rice.
While the rice cooks, peel and finely chop the onion. Warm a deep frying pan for 2 mins over a medium heat, then add 1 tbsp oil and the onion. Season with a pinch of salt and pepper. Fry for 5 mins, stirring now and then, till the onion starts to soften and look glossy.
While the onion fries, peel and crush or grate the garlic. Dice the tomatoes.
Stir the garlic into the onion. Cook and stir for 1 min, then add the tomatoes. Season with a pinch more salt and pepper and cook for 5 mins, stirring once or twice till the tomatoes have started to collapse.
While the tomatoes cook roughly chop the olives. Pick the oregano leaves off the stems and roughly chop them.
Stir the olives and most of the oregano into the tomatoes. Crumble in the stock cube and pour in 300ml water. Pop a lid on the pan and simmer for 10 mins.
While the tomato sauce simmers, slice any really thick cores out of the rainbow chard and shred the leaves.
Stir the rainbow chard and stalks into the tomato sauce. Simmer, with the lid off, for 3 mins to start to wilt the chard. Slide the haddock fillets into the tomato sauce - you can halve the fillets if that helps them fit in your pan. Put the lid back on the pan and gently cook the haddock in the tomato sauce for 3-5 mins. The fish should be white, opaque and easily flake when pressed with a fork.
Fluff the ric eup with a fork and divide between 2 warm plates. Serve the haddock, tomato and chard sauce with the rice, garnished with the last of the oregano.