Adjust the oven rack to the middle position and preheat the oven to 350 degrees Fahrenheit. Grease and flour a 9×13-inch pan (true to size—not disposable) and set aside.

Whisk together the flour, baking powder, baking soda, and salt in a large mixing bowl. Add the margarine and mix with an electric mixer on the slowest speed until the mixture turns into crumbs. Measure out one cup of the crumb mixture and set aside.

Add the eggs, whip, and vanilla and stir briefly to combine. Beat at medium speed until the batter is smooth, about 30 seconds. Scrape the batter into the prepared pan and sprinkle the reserved crumbs evenly over the top.

Bake for 40 minutes, rotating halfway through baking, until the cake is golden brown and feels set when pressed lightly in the center.

Cool completely in the pan.