WHAT YOU NEED

First make the pastry. Put the flour, baking powder, ground almonds, coconut oil, sugar and salt into large bowl. Rub together with your fingertips until the mixture resembles breadcrumbs. Now add the aquafaba and use your hands to bring the dough together. Keep kneading until soft and smooth, then shape the dough into a ball, wrap in plastic wrap (or eco-wrap) and chill in the fridge for 20 minutes.

Preheat the oven to 180°C (350°F) and lightly oil a baking tray measuring about 30 cm x 20 cm (12 inches x 8 inches).

On a flour-dusted surface, roll out the dough into a rectangle roughly the same size as your baking tray. Gently lay the pastry in the tray, pressing it out evenly. Use a fork to prick the pastry all over, then bake for 15 minutes or until lightly golden.

Meanwhile, toast the nuts and brown sugar in a dry frying pan over a medium heat, stirring often, until they begin to caramelise. Set aside to cool.

For the crumble topping, put all the ingredients in a bowl and rub together with your fingertips until they resemble coarse breadcrumbs.

Remove the pastry base from the oven and set aside to cool, then turn the oven down to 160°C (315°F).

Next make the meringue by whisking the aquafaba to soft peaks. Slowly add the sugar and keep whisking until you have a smooth and glossy meringue that stands in stiff peaks.

When the pastry base has been cooling for about 15 minutes, spread with the jam. Put the rhubarb in a bowl and toss with the rosewater, then arrange in rows on top of the jam. Place the caramelised nuts in the gaps between the rhubarb. Spoon over the meringue, spreading it out evenly, then sprinkle with the crumble topping.

Bake for 1¼ hours until the meringue is cooked and the rhubarb is tender.

Allow to cool completely in the tin; as this tart is quite wet, you may want to serve it directly from the tin as well. Scatter with the rose petals, if using, just before serving.