Heat the oven 200°C/GM6. Roll defrosted pastry out thinly on a floured surface and line a fluted flan tin. Prick base all over with a fork and chill for ½ an hour. Line the pastry case with a sheet of crumpled baking paper and fill with ceramic baking beans. Place on a hot baking sheet and bake for 15 minutes. Remove the lining paper and beans and bake for a further 5-10 minutes until the pastry is pale golden. Reduce the oven temperature to 190°C/GM5.
Heat a pan over medium heat with the coconut oil. Add sliced onion and cook for a couple of minutes without colour until softened, then add grated garlic and cook for another minute. Add the balsamic vinegar, stir, and remove from the heat. Stir in the rocket leaves to wilt slightly and set aside. Peel and finely slice golden beetroot and deep fry until crispy, drain and season with salt.
Grate the potato, rinse under cold water and wring dry in a tea towel removing as much moisture as you can then place in blind-baked crust, spreading evenly. Grate beetroot and remove excess moisture as per step above and layer over the potatoes, reserving a handful to top the tart. Whisk together eggs, crème fraiche, cayenne pepper and season with salt and pepper. Stir in the onion and greens mixture, then pour into the tart base. Top with the reserved beets around the edges.
Bake for 35-45 minutes until the centre of the tart is firm to the touch. Serve hot with a golden beetroot crisps, beetroot glaze and rocket leaf salad
Top tip: Swap the rocket with picked watercress leaves for an enhanced peppery flavour
Top tip: Use vinyl gloves (890085) when handling beetroot to prevent staining your hands