Preheat your oven to 350°F (175°C) and grease your baking pan thoroughly. Line with parchment paper for easy removal.

In a medium bowl, whisk together flour, cornstarch, baking powder, baking soda, and salt. This ensures even distribution of leavening agents.

In a large bowl, beat butter and sugar together for 3–4 minutes until light, pale, and fluffy. This step helps incorporate air into the batter.

Add vegetable oil and continue mixing until fully combined. The oil ensures a moist texture.

Add eggs one at a time, mixing well after each addition to create a smooth batter.

Mix in vanilla extract, lime zest, and lime juice. The zest adds concentrated citrus flavor while juice provides tang and tenderness.

If using food coloring, add it now and mix until evenly distributed.

Add half of the dry ingredients to the wet mixture and mix gently.

Pour in the milk and mix until just combined.

Add the remaining dry ingredients and fold gently using a spatula to avoid overmixing.

Pour the batter into the prepared pan and spread evenly.

Tap the pan lightly on the counter to remove air bubbles.

Bake for 30–35 minutes or until a toothpick inserted in the center comes out clean.

Remove from the oven and allow the cake to cool in the pan for 10–15 minutes.

Transfer to a cooling rack and let it cool completely before adding glaze.

In a small bowl, prepare the glaze by mixing powdered sugar, lime juice, milk, and zest.

Whisk until smooth and pourable but slightly thick.

Pour the glaze over the cooled cake, spreading gently if needed.

Let the glaze set for 10–15 minutes before slicing.

Slice into squares and serve for best texture and flavor.