Cream the room temperature butter and granulated sugar in a mixing bowl until light and fluffy, about 2–3 minutes.

Add in a large egg and pure vanilla extract, mixing until fully incorporated and smooth.

In a separate bowl, whisk together all-purpose flour, baking soda, and fine sea salt, then set aside.

Divide the creamed mixture into two bowls. Sift matcha powder into one and mix until incorporated.

Roll tablespoons of each dough together to create a marbled effect.

Chill the marbled dough in plastic wrap for 20–30 minutes.

Preheat the oven to 350°F (175°C). Line a baking sheet with parchment paper and place dough balls 2 inches apart, flattening them slightly.

Bake for 10–12 minutes until edges are golden and centers are soft. Allow to set for 5 minutes before cooling on a wire rack.