1. To make the pastry, place the Pure dairy free sunflower spread in a food processor with the icing sugar, salt, whole egg and lemon zest, and blend for 20 seconds. Add the ground almonds and flour and blend until the dough just comes together. Place in a polythene bag and chill for at least 2 hours.
2. Preheat the oven to 180°C. Take the pastry out of the fridge and quickly press up the sides and into the shape of a 23cm loose-bottomed flan tin. Keep or discard any excess pastry.
3. Lightly prick the base with a fork in several places. Line the pastry with a circle of parchment paper and fill with baking beans. Chill for 15 minutes, then bake-blind for another 12 minutes. Remove from the oven and take out the beans and paper. Beat the egg yolk and use to brush the base, then bake for another 8 minutes until lightly golden to form a glaze.
4. Meanwhile, mix together the ingredients for the filling in a bowl. Place the flour, oat flakes and sugar for the crumble topping in a separate bowl and rub in the Pure dairy free sunflower spread.
5. Reduce the oven to 150°C, spoon the filling into the glazed pastry crust and sprinkle the crumble on top. Bake for 35-45 minutes or until the filling has cooked down and the crumble topping is crisp and lightly golden. Allow to cool for 5 minutes, then carefully lift out of the flan tin. Score the tart into portions and, using a tea strainer as a sieve, dust with icing sugar. Cut into slices and arrange on plates with some of the dairy-free vanilla ice cream to serve.