Ingredients
1 box (15.25 ounces) yellow cake mix
Directions
Preheat your oven to 350°F (175°C). Lightly grease a 9×13-inch metal baking pan with nonstick spray or butter, making sure to coat the corners so the cake releases easily.
In a large mixing bowl, combine the dry yellow cake mix and the instant lemon pudding mix. Whisk them together so the pudding is evenly distributed through the cake mix; this helps the cake bake up uniformly tender.
In a separate medium bowl or large measuring cup, whisk together the cold whole milk, neutral oil, eggs, granulated sugar, and vanilla extract until the mixture is smooth and the sugar is mostly dissolved. The milk and extra sugar are key to Aunt Barbara’s moist, almost custardy texture.
Pour the wet mixture into the bowl with the cake and pudding mixes. Add the finely grated lemon zest. Using a hand mixer on medium speed or a sturdy whisk, beat until the batter is thick, smooth, and glossy, about 2 minutes.
Scrape down the sides and bottom of the bowl once or twice to catch any dry pockets.
Transfer the batter to the prepared 9×13-inch metal pan. The batter will be quite thick; use a spatula to spread it into the corners. Then, lightly drag the spatula in loose swirls across the top so the surface looks slightly uneven and textured—that’s what gives the baked cake its homey, swirled appearance.
Bake on the center rack of the oven for 28 to 34 minutes, or until the top is lightly golden, the center looks softly set, and a toothpick inserted near the center comes out with a few moist crumbs but no wet batter. The cake should feel springy but not dry when gently pressed.
Remove the pan from the oven and place it on a wire rack. Let the cake cool completely in the pan; this helps it finish setting into that soft, almost pudding-like crumb with little moist pockets throughout.
Once cool, you can dust the top lightly with powdered sugar or spread with softly whipped cream just before serving, if you like. Cut the cake into squares right in the pan and serve directly from the metal pan for that classic family-gathering feel.
Store leftovers covered in the refrigerator for up to 4 days; the cake stays wonderfully moist.
Variations & Tips
For a stronger citrus punch, replace 2 to 3 tablespoons of the milk with freshly squeezed lemon juice and add an extra teaspoon of lemon zest. If you like a more pronounced tang, drizzle the cooled cake with a simple lemon syrup made by simmering equal parts lemon juice and sugar until just dissolved, then spoon it over the surface and let it soak in for 10 to 15 minutes before serving.
For a slightly lighter texture, you can use 2% milk instead of whole milk, though whole milk gives the richest, most custardy crumb. A white cake mix can stand in for yellow if that’s what you have on hand; it will give a paler, slightly more delicate cake.
To dress it up for a brunch or shower, top each slice with a dollop of whipped cream and a few fresh berries. If you prefer a frosted finish instead of powdered sugar, beat together 4 ounces of softened cream cheese, 2 tablespoons softened butter, 1 1/2 cups powdered sugar, a pinch of salt, and 1 to 2 tablespoons milk or cream plus a little lemon zest, then spread it over the cooled cake in loose swirls to echo the rustic, uneven look of the baked surface.