Prepare the rhubarb:Place 400 g rhubarb in the baking dish and sprinkle with half of the 100 g sugar and the 1 tsp vanilla sugar.
Make the crumble topping:In a bowl, mix 100 g wheat flour, 50 g rolled oats and the remaining 50 g of sugar.Add 75 g butter in cubes and rub it into the flour mixture until it resembles coarse crumbs. Stir in 50 g flaked almonds.
Assemble:Sprinkle the crumble topping evenly over the rhubarb.
Cooking in the air fryer:Place the dish in the air fryer and bake at 180°C for about 15-20 minutes, or until the top is golden and crispy.Start the online kitchen timer here
Serving:Let the rhubarb crumble cool for 10 minutes before serving.Serve with vanilla ice cream or crème fraîche.
Notes
Season the crumble with a little extra sugar if the rhubarb is very tart.