Preheat the oven to 180°C (350°F). Butter a 23 cm (9 inch) pie plate.
In a large bowl, whisk the eggs. Add the cheese, basil, and the sundried tomatoes. Season with salt and pepper. Stir to combine. Set aside.
In a cast-iron, oven-safe skillet set over medium heat, sauté the zucchini and leek. Season with salt and pepper.
Pour the egg mixture into the pan and stir thoroughly. Bake in the centre of the oven for approximately 25 minutes, or until the frittata is golden brown.