1-Preheat oven to 350°F (175°C) with a rack in the center. Line a 9-inch baking pan with parchment paper or spray with non-stick baking spray to prevent sticking.

2-In a bowl, stir melted butter and sugar together until well combined. Add vanilla extract and eggs; mix until the mixture is smooth and creamy.

3-In a separate bowl, sift together flour, espresso powder, baking powder, and salt. Whisk thoroughly to ensure everything is evenly distributed.

4-Add the dry ingredients to the wet ingredients and mix into a soft dough, being careful not to overmix.

5-Spread the dough evenly into the prepared pan, making sure it reaches all corners for uniform baking.

6-Bake for 28 to 30 minutes. The edges should be set, the top golden brown and slightly puffed, but the inside under the crust will appear underdone to keep it moist avoid overbaking.

7-Remove from oven and place the pan on a cooling rack. Allow it to cool completely before cutting into squares for the best texture.