Place the flour and butter in a food processor. Process until the mixture resembles fine breadcrumbs. Add the egg yolk and water and process until dough just comes together, adding more water if needed. Turn the dough onto a lightly floured surface and gently knead until just smooth. Shape into a disc. Cover with plastic wrap and place in the fridge for 30 mins to rest.
Preheat oven to 200°C. Wrap each beetroot in foil. Place on a baking tray. Line another baking tray with baking paper. Arrange the tomatoes, pumpkin and carrots in a single layer on the lined tray. Spray with olive oil spray. Season. Roast the beetroot for 10 mins. Add the tomato mixture to the oven. Roast with the beetroot for 20 mins or until the beetroot, pumpkin and carrots are tender and tomatoes begin to collapse.
Roll the pastry out on a lightly floured surface to a 3mm-thick disc. Line a 24cm (base measurement) fluted tart tin with removable base with the pastry. Use a small sharp knife to trim excess. Place in the fridge for 15 mins to rest.
Heat a medium frying pan over medium heat. Spray with olive oil spray. Add the leek and cook, turning, for 3-4 mins or until leek is just tender. Set aside to cool slightly.
Line the pastry with baking paper and fill with pastry weights or rice. Place on a baking tray. Bake for 10 mins. Remove the paper and weights or rice. Bake for a further 10 mins or until light golden. Reduce oven to 160°C.
Whisk the eggs, cream and cheddar in a medium bowl. Season. Remove the foil from the beetroot. Wearing gloves to avoid staining your hands, peel and cut into halves. Arrange over the base of the tart case with the pumpkin, carrot, leek and zucchini. Pour the egg mixture around the vegetables in the case. Sprinkle with the goat’s cheese.
Bake for 30-35 mins or until the filling is just set. Remove from oven and set aside for 5 mins to cool slightly.
Transfer the tart to a serving platter. Top with the tomatoes and thyme. Cut into wedges and serve warm or at room temperature.