Preheat the oven to 375° F (190° C). Line baker's half baking sheet (about 16.5 x 11.5 inches) with parchment paper.
In a small bowl, mix matcha powder with 1 tablespoon hot water until smooth.
Separate egg yolks and egg whites. (Tip: Make sure there's absolutely no trace of egg yolk in egg whites, or it won't whip into fluffy white stiff peaks.)
In a separate medium bowl, whisk the egg yolks and ¼ cup of sugar until pale and tripled in size, about 2 minutes.
Mix in the matcha paste.
In a mixing bowl with whisk attachment, beat the egg whites on medium speed until frothy. Add remaining ¼ cup of sugar one tablespoon at a time. Increase the speed to medium high and continue to beat until stiff peaks form.
Add half of whipped egg whites into the egg yolk mixture. Gently fold the batter with a spatula until almost smooth, and then add the remaining whipped egg whites. Carefully fold the batter until smooth.
Sift in the cake flour and salt. Gently fold it until the flour is fully incorporated.
Pour the batter into the prepared baking pan. Using an offset spatula, spread the batter evenly and smooth the surface.
Bake for 8-10 minutes, or until inserted toothpick comes out clean.
Meanwhile, lay a clean kitchen towel on the counter and generously dust with powdered sugar.
Once the cake is out of oven, immediately invert it on the prepared kitchen towel. Peel off the parchment paper and roll it with the towel and all. (This helps the cake roll without cracking by creating a muscle memory.) Set the rolled cake on a cooling rack and cool completely.