Preheat your oven to 180°C (350°F) and line an 8x8 inch baking dish with parchment paper.

Grate the zucchinis and squeeze out excess moisture using a clean kitchen towel or cheesecloth.

In a large mixing bowl, combine self-raising flour, salt, and pepper. Add chopped onion and fold in grated cheddar cheese.

Mix drained zucchini into the dry ingredients using a spatula, folding until just combined.

In a separate bowl, whisk together eggs, vegetable oil, and chopped parsley until well combined.

Pour the wet mixture into the dry ingredients and stir gently until just combined.

Transfer the batter to the prepared baking dish, spreading evenly with a spatula.

Bake for 30-35 minutes until golden brown and a toothpick inserted in the center comes out clean.

Allow to cool in the dish for about 10 minutes before transferring to a wire rack.

Slice into squares and serve warm or at room temperature.