Preheat the oven to 350F and line a loaf pan with parchment paper.
Next, add the matcha and hot water to a small bowl and whisk together until smooth. Set aside for later.
Add the oat milk, sugar, applesauce, olive oil, apple cider vinegar, and vanilla to a large mixing bowl. Then, whisk together until smooth.
Next, add the dry ingredients to the bowl starting with the all-purpose flour and then layering the cornstarch, baking powder, baking soda, and salt on top. Gently whisk together into a smooth batter, though keep in mind some clumps are okay.
Take 1 ½ cups of the batter and add it to a separate large mixing bowl. Then, add the dissolved matcha to the bowl and use a spatula to fold and combine until the batter is completely green.
Next, use two cookie scoops or large spoons to alternate dollops of the vanilla batter and matcha batter into the parchment lined loaf pan. This helps to create the swirls when the bread bakes.
Add the pan to the oven and bake for 48-52 minutes until cooked through and browned on top.
Take the loaf pan out of the oven, cool in the pan for 5 minutes, then remove and place the bread onto a wire rack to cool completely before slicing. Slice the cooled cake into 8 slices using a serrated knife and enjoy!