To make a boxed lemon cake mix taste like it came from a professional bakery, swap the water for whole milk (or half water and half fresh lemon juice), trade vegetable oil for melted butter, add one extra egg, and mix in a small box of dry instant lemon pudding.
Boost Moisture and Richness
Use melted butter: Swap the oil called for on the box for an equal amount of melted, cooled butter for a richer flavor.
Add dairy: Replace water with whole milk, buttermilk, or full-fat sour cream to create a dense, velvety crumb.
Add an extra egg: Put in 4 eggs instead of the usual 3 to add structure and a rich, pound-cake-like texture.
Intensify the Lemon Flavor
Instant pudding mix: Stir in half a box (about 3.4 oz) of dry instant lemon pudding mix directly into the dry cake mix.
Fresh zest and juice: Fold in 1 to 2 tablespoons of freshly grated lemon zest and a splash of fresh lemon juice to brighten the flavor.
Lemon extract: Add 1 teaspoon of pure lemon extract for a punchy, authentic citrus note.
Finishing Touches
Poke glaze: While the cake is still warm, poke holes across the top with a fork and pour a simple glaze made of powdered sugar and fresh lemon juice over it.