Step 1Heat the olive oil in a large non-stick frying pan over medium heat. Sauté chopped onion for 5 minutes, or until softened. Add the garlic and lemon zest and cook, stirring, for 1 minute, or until fragrant. Add silverbeet and zucchini and cook, stirring, for 3–4 minutes, or until just wilted. Transfer to a colander placed over a bowl to drain any excess liquid, pressing down on the silverbeet with the back of a spoon. Set aside to cool.
Step 2Whisk 4 of the eggs and the ricotta together in a large bowl until smooth. Stir through the cooled silverbeet mixture, feta and chopped herbs.
Step 3Preheat oven to 160ºC. Spray a 16cm x 26cm rectangular slice tin with olive oil. Spray one sheet of filo lightly with oil, top with another layer of filo and repeat process to make a stack of 6 filo sheets. Line prepared tin with filo stack, allowing excess pastry to overhang the sides. Spoon filling into pastry base, and smooth the surface with the back of a spoon. Roll the edges of the filo pastry over to form a border.
Step 4Make 2 indents on top of the filling with a spoon. Carefully break the remaining 2 eggs into the indents. Bake the tart for 40–45 minutes, or until pastry is golden and filling is set.
Step 5Place salad leaves, tomatoes and cucumber in a salad bowl. Add balsamic vinegar and toss gently to combine. Serve tart with the garden salad.