Preheat your oven to 350°F (175°C) and grease a 9×13-inch baking pan.

In a large bowl, whisk together flour, sugar, baking powder, and salt.

In another bowl, beat eggs and mix in oil, vanilla, pineapple, and mandarin oranges until well combined.

Pour the wet mixture into the dry ingredients, gently folding until just mixed.

Pour batter into the prepared pan and smooth the top.

Bake for 30-35 minutes or until golden brown; a toothpick inserted should come out clean.

Cool in the pan for ten minutes before transferring to a wire rack.