Preheat oven to 300F and butter a loaf pan very well.
In a small bowl, whisk matcha powder and hot water together until smooth. Set aside.
In a medium bowl, whisk together almond flour, protein powder, baking powder, baking soda and salt. Set aside.
In a large bowl, beat butter until smooth. Add granulated erythritol and beat until lighter and well-combined, about 2 minutes. Beat in eggs, one at time, scraping down beaters and sides of bowl with a rubber spatula as needed. Beat in stevia extract.
Beat in half of the almond flour mixture, then beat in almond milk. Beat in remaining almond flour mixture until well combined.
Remove half of the batter to another bowl. With one half of batter, beat in matcha mixture until well combined. With the other half of the batter, beat in almond extract.
Alternate putting large spoonfuls of each batter into the prepared pan. Using a knife, swirl the batters together. Smooth the top.
Bake 60 minutes, or until top is deep golden brown and a tester inserted in the center comes out clean. Let cool in pan 5 minutes, then flip out onto a wire rack to cool completely.
Notes
Serves 12. Each serving has a total of 7.1 g of carbs and 3.2 g of fiber. Total NET CARBS = 3.9 g.