Preheat oven to 350 degrees F.
Cream butter, sugar, and salt until light and fluffy. I recommend using a hand mixer instead of stand mixer for this stage due to the small amount of butter.
Add egg and mix to emulsify.
Whisk flour and matcha together.
Alternate adding in the milk and flour mixture in parts. Mix only until fully incorporated. If you overmix, your cake may not rise well and may have weird bubbles and holes.
Add vanilla extract and drop of green food coloring (if using) and mix to incorporate.
Pour batter into a greased 8 inch cake pan. I always line the bottoms of my cake pans with parchment paper. Bake for 25 minutes or until a skewer inserted into the center comes out clean.
Let cake cool completely. The crumb will be very soft, so be gentle turning it out of the pan. Frost with your favorite frosting.