Preheat your oven to 350°F and prepare an 8-inch square baking pan by lining it with parchment paper and greasing lightly. While the oven heats, bloom the matcha powder by whisking it with 1 tablespoon of sugar and 1 tablespoon of water in a small bowl until completely smooth and lump-free. This step is essential for distributing the matcha evenly throughout the batter and preventing clumpy texture in your final bars.

In a large mixing bowl, beat together the melted and cooled butter, remaining sugar (3/4 cup minus 1 tbsp), lemon zest, and salt for 3-5 minutes until the mixture is light, fluffy, and pale. This creaming process incorporates air and creates a tender crumb structure. The lemon zest adds a subtle brightness that balances the earthiness of matcha—this is key to preventing the bars from tasting too grassy or one-dimensional.

Add the egg, egg yolk, oil, and vanilla extract to the creamed butter mixture and beat for about 1 minute until well combined and emulsified. Pour in the matcha liquid from Step 1 and stir for 1 minute until the batter turns a beautiful bright green and the matcha is fully incorporated. Don't overmix at this stage—you want to combine ingredients but not develop the gluten in the flour, which would make the bars tough.

Sprinkle the baking powder and flour over the wet batter and fold together gently with a spatula until just combined—stop as soon as you don't see dry flour streaks. Pour the batter into your prepared pan and spread it into an even layer. Bake for 18-22 minutes until an instant-read thermometer inserted into the center reads 190°F. The bars should look set but still slightly tender.

Remove the pan from the oven and let the bars cool in the pan for 30 minutes. Transfer the entire cake (still on parchment if desired) to a wire rack and cool for an additional 20 minutes until completely cool to the touch. This cooling time is important—if you frost warm bars, the frosting will melt and slide off.

In a clean bowl, beat the room-temperature butter and a pinch of salt for 1-2 minutes until smooth and creamy. Add the sifted powdered sugar and cream, then beat for 2-3 minutes until light and fluffy. I like to sift my powdered sugar beforehand to prevent lumpy frosting—it makes a huge difference in texture and spreadability. The frosting should be thick but spreadable; if it's too soft, refrigerate it for 5-10 minutes before frosting.

Spread the matcha cream frosting evenly over the cooled bars using an offset spatula or the back of a spoon. For an elegant finish, lightly dust the frosted surface with additional matcha powder using a fine-mesh sieve. Cut into squares and serve—the bars will keep in an airtight container at room temperature for 2-3 days, or refrigerated for up to a week.