To make the pastry, start by using an electric whisk to combine the plain flour with the thyme leaves, a sprinkle of salt and icing sugar. Next add 220g butter combining on a low speed until you have a rough crumb. Add in 1 beaten egg and an extra egg yolk.
When the pastry starts to come together, add in roughly 3-4 tbsp ice cold water a tablespoon at a time just enough so that the pastry forms into a smooth ball. If you add too much you can add a little extra flour to bring it back to the right texture.
Remove the dough from the food processor, roll it out and line a 24–26cm / 9½ – 10in tart tin to around 3mm thick. Prick the pastry all over with a fork and allow to rest in the fridge for around 30 minutes before baking. Meanwhile, preheat the oven to 180˚C.
To make the filling, beat together 200g butter and the golden caster sugar until light and fluffy then add in the four eggs one at a time, continuing to beat. Gently fold in the almonds. Pour the mixture into the pastry case. Place the tart into the oven and allow to cook for around 50-60 minutes until cooked through. Remove from the oven and allow to cool.
For the rhubarb jam, combine the rhubarb, orange peel, vanilla paste, star anise, 250ml water and 250g caster sugar over a medium to high heat cooking until the sugar dissolves (the rhubarb should be boiling at this stage). Allow to boil for around 10 minutes then reduce the heat and allow to simmer for around 15 minutes until the rhubarb had softened and has begun to set slightly. Test if the jam has reached setting stage by taking a teaspoonful and placing on a plate. Leave it for a short while (30 seconds or so) to see if it sets. Once it does this, remove from the heat and allow to cool before spooning onto the top of the tart.
For the meringue, combine the 170g egg whites, 255g sugar, 1 tsp salt and lemon juice in a bowl and stir over a bain marie for 10 minutes until the texture is frothy and smooth between your fingers. Transfer to your food processor where you can whisk it on a high speed for around 5 minutes until you have a thick, glossy and smooth consistency. Spoon onto the top of the rhubarb arranging soft peaks with the back of a spatula. Using a kitchen torch, briefly torch the meringue until you achieve a golden finish.
Your dessert is now ready to serve.