Preheat the oven to 180 C / Gas 4. Grease and lightly dust with flour a 23cm springform tart tin.
For the shortcrust pastry:
In the food processor, combine flour, flax seeds and salt and pulse to mix. Add water and oil, and pulse several times until a soft dough ball is formed. Roll out over a lightly floured surface into a large circle. Line the prepared tart tin by pressing the pastry gently into the base and sides then prick case with a fork.
Bake in the preheated oven for 5 minutes. Remove from the oven and let it sit. Keep the oven switched on.
For the filling:
Meanwhile, heat olive oil on a medium frying pan over medium heat. Sautee onions and red peppers until tender then add cubed courgettes, aubergine and tomatoes. Stir gently over low heat until tender. Add crumbled vegetable stock cube for extra flavour.
Mix in grated carrot and cook for another 5 minutes. Remove from heat and transfer to a bowl. Add grated cheese and beaten eggs then season with salt and pepper and mix well. Pour mixture into pastry base.
Bake in the preheated oven for 35 minutes, or until set in the centre and slightly golden. Remove from the oven and serve warm or allow to cool before serving.