Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, combine the cake mix, crushed pineapple (with its juice), vegetable oil, and eggs. Beat with a mixer on medium speed for 2–3 minutes, until smooth and well combined. Pour the batter into the prepared pan and smooth the top with a spatula.
Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool completely in the pan before adding the topping.
