Heat the oven to 180°C / 350°F with the fan.
In a pan, sauté the onions with the olive oil until they are tender and change color.
Set aside to cool.
Grate the zucchinis into a bowl.
Add salt, pepper, eggs, flour and baking powder and mix well with the zucchinis.
Add the cooled onions and mix well.
Grease a baking pan (I used a 9.5-inch round glass pan, although any type of pan will work.)
Sprinkle the breadcrumbs on the greased pan evenly.
Pour the batter into the pan.
Bake for 40 minutes.
Cool at room temperature and serve.