Preheat the oven to 350°F (175°C). Grease a 9×13-inch baking pan or line it with parchment paper.

In a large mixing bowl, cream together the butter and sugar until light and fluffy (about 3 minutes). Add eggs one at a time, mixing well after each addition, then stir in vanilla extract.

In another bowl, whisk together flour, baking powder, and salt. Gradually add dry mixture to wet ingredients, stirring until just combined.

Incorporate green food coloring until you achieve your desired shade of green.

Spread the batter evenly in the prepared baking pan and bake for 20-25 minutes or until golden brown. A toothpick inserted into the center should come out clean.

Allow to cool completely in the pan on a wire rack before cutting into squares.