Preheat the oven to 220°C/gas mark 7. Spread the rhubarb in a single layer in a large ovenproof dish. Add the orange zest and juice and 3 tbsp water, then scatter over 175g sugar. Stir, then cover with kitchen foil and bake for 20-25 minutes until soft.
Remove from the oven and cool completely. Meanwhile, put the flour and butter in a bowl and rub together using your fingertips until it resembles rough breadcrumbs. Mix in the remaining sugar and nuts and tip on to a foil-lined baking tray. Bake for 10-12 minutes, turning the mixture halfway, until golden. Set aside.
Drain the rhubarb in a sieve over a bowl. Transfer the juices to a pan, bring to the boil, then simmer until syrupy. Leave to cool. In a separate bowl, whisk the cream with the icing sugar until the beaters leave a soft trail in the mixture, then fold in the yogurt.
Divide the creamy yogurt between the bowls. Add the rhubarb and syrup, then scatter over the nutty streusel.