Preheat your oven to 350°F (175°C) and prepare your loaf pan by greasing it generously with butter or lining it with parchment paper.

In a large mixing bowl, cream together the unsalted butter and sugar with an electric mixer until the mixture is light and fluffy.

Add the room temperature eggs one at a time, mixing well after each addition until the batter is smooth.

In a separate bowl, whisk together the all-purpose flour, baking powder, and a pinch of salt.

Gradually add the dry ingredients to the wet mixture, alternating with the milk until fully combined.

Divide the batter into two equal bowls. In one, gently fold in the matcha powder.

Spoon alternating dollops of the matcha and plain batter into your prepared loaf pan and swirl gently with a knife.

Bake for 50-60 minutes, checking for doneness with a toothpick.

Let the cake cool for about 10 minutes in the pan, then transfer to a wire rack to cool completely.