A thyme-flavoured pastry case is a container for nutrition-packed vegetables: tomatoes, onions and zucchini with vitamin C, as well as anti-oxidants beta carotene and lycopene to fight against cancer and heart disease.
Coat a large non-stick frying pan with oil and set over medium-high heat until hot. Reduce heat to medium-low. Add onion; sauté until very soft and golden, 20 minutes. Transfer to a plate.
Preheat oven to 200°C. Mix flour, thyme and half the salt in a large bowl. Mix in water and oil just until a soft dough forms. Lightly sprinkle work surface with flour and pat out dough into a 35 x 25 cm rectangle or 32 cm round. Fold in half and transfer to 32 x 22 cm tart pan or 28 cm round tart pan with removable base. Trim the edges.
Cut zucchini diagonally into long, 2.5 cm-thick slices. Coat frying pan again with oil and set over medium heat. Add zucchini and sauté until golden, 5 to 7 minutes.
Arrange zucchini, tomato and onion in rows on the pastry base, standing them up and overlapping them slightly. Sprinkle with remaining salt and all the parmesan. Bake until crust is golden, about 20 minutes. Serve warm or at room temperature.