Preheat the oven to 200°C. Grease a 35 x 13cm rectangular tart tin or a 24cm round tart tin with non-stick spray.
1. Crust: Toast the seeds in a dry pan until the colour starts to change. Remove and set aside to cool.
2. Add the flour, icing sugar and salt to the bowl of a food processor and pulse until mixed. Add the butter and pulse until the mixture resembles breadcrumbs.