Salt the Zucchini: Toss the grated zucchini with a generous pinch of salt in a colander or bowl, then let it sit for at least 5 minutes. This draws out the excess moisture that would otherwise leave your bake watery in the centre.

Roast the Sweet Potato and Onion: Spread the sweet potato ribbons and onion rings across a parchment-lined baking sheet in a single layer. Spray lightly with avocado oil and season with a pinch of salt. Roast at 400°F (200°C) for 15–20 minutes, until the edges are turning golden and slightly caramelized.

Make the Egg Mixture: While the vegetables roast, whisk together the egg whites, whole eggs, Greek yoghurt, Parmesan, Dijon mustard, garlic powder, and a good pinch of pepper until smooth and well combined.

Prepare the Zucchini: Once the sweet potato is out of the oven, reduce the temperature to 350°F (175°C). Squeeze the salted zucchini firmly in a clean kitchen towel to remove as much liquid as possible this step matters more than it looks like it should.

Assemble: Set aside a few of the prettiest roasted sweet potato ribbons for the top. Fold the squeezed zucchini, the remaining sweet potato ribbons, and the roasted onion into the egg mixture until evenly distributed.

Bake: Pour the mixture into a parchment-lined 8 x 8-inch baking dish. Arrange the reserved sweet potato ribbons decoratively across the top. Bake at 350°F (175°C) for 50–60 minutes, until the centre is set, a knife inserted comes out clean, and the top is lightly golden.

Rest and Serve: Let the bake rest for 10 minutes before slicing this keeps it from crumbling and lets the centre finish setting. Slice into squares and serve warm, or let it cool completely for meal prep.