Preheat the oven to 180 degrees Celsius (350 degrees Fahrenheit).
Combine all ingredients in a large bowl along with about 7 tablespoons of water, until it forms a firm dough - add the water a few tablespoons at a time so that you don’t add too much! You can keep this pastry dough in the fridge for up to a day if you like, but there is no need to chill it before using.
Place the pastry dough into a greased pie dish and use your fingers to carefully press it across the bottom and up the sides of the dish - I used a 22.5cm/9inch pie dish.
Use a fork to pierce the surface (remember the sides too!) of the pastry, so that it doesn’t puff up in the oven. Alternatively, you can use baking beans.
Bake in the oven for around 30 minutes, until the pastry crust is firm to the touch and golden brown.
Leave to cool slightly before pouring in the filling.
For the lemon custard:
Measure out the milk in a jug or measuring container.
Pour the milk into a pan, leaving behind a few tablespoons of milk in the jug.
Heat up the milk in the pan.
Add the custard powder to the remaining milk in the jug and mix well, ensuring it has dissolved completely.
Once the milk in the pan is steaming, add approximately half of the hot milk to the bowl with the dissolved custard powder, mix well and transfer the custard powder mixture to the pan.
Mix well and keep stirring on a low heat for around 5 minutes, until thickened.
Add the lemon juice and maple syrup.
Taste and add extra lemon juice or maple syrup if desired.
To assemble:
Once the tart crust has cooled a little, carefully pour the filling into the crust.
Leave to cool completely before cutting, keeping the tart in the fridge for few hours to allow the filling to set properly.
Keeps covered in the fridge for up to a few days.
Video
Notes
*You can alternatively use almond flour.**You can use any type of plant-based milk, though results do vary depending on which one you choose. I like to use unsweetened cashew milk. Cashew, oat or coconut milk make a super thick and creamy custard, whilst almond milk will be less creamy. Rice milk creates a just-set lemon curd-like consistency.***If you can’t get hold of a shop-bought custard powder, you can replace it with the same amount cornflour (cornstarch) or arrowroot, which will result in the same texture, though the colour will be considerably less yellow. To add yellow colour, I would suggest adding a tiny pinch of saffron, which I much prefer to turmeric as it has a much milder flavour.