Preheat the over to 350F (180C). Butter an 8x8 baking dish.
In a big bowl whisk together the eggs and the sugar just until it all comes together, about 30 seconds, no more.
Add the flour (and baking powder if using) and wisk together just until the flour disappears and there are no more lumps, about 45 seconds, no more. The batter will be quite thick and there won't be a lot of it.
Spread the fruit over the bottom of the dish and spread the batter over. It will barely cover the fruit and it'll look like it's not enough, but it will be great. Alternatively you can mix the fruit with the batter.
Bake for 45-55 minutes depending on your oven. A toothpick inserted into the cake should come out clean when the cake is ready.