Mash the bananas in a large mixing bowl. Add the oil, eggs and vanilla and mix well. Stir in the sugar.
2 large bananas, ⅓ cup (80ml) vegetable oil, 2 large eggs, 1 tsp vanilla extract, 1 cup (200g) sugar
Sift in the flour, baking powder and salt. Fold until no dry streaks remain – don't over-mix.
2 cups (250g) flour, 1 ½ tsp baking powder, ¼ tsp salt
Divide the batter evenly between two bowls.
Place the buttermilk in a small jug. Add the matcha and mix with a coffee frother or small whisk until smooth and lump-free.
¼ cup (60ml) buttermilk, 1 tbsp matcha powder
Fold the matcha buttermilk into one bowl until evenly green. Add a drop of pandan extract or green food gel if you want a brighter color.
Pandan extract or green food gel
Bake in Oven or Air Fryer
Spoon or pipe alternate dollops of the two batters into a greased and lined 2 lb (900g) loaf pan. Push a skewer or butter knife down to the bottom and draw two or three figure-eights along its length to create the marble swirl. Tap the pan on the counter to level the top.
Oven: bake at 340°F (170°C) for 50–60 minutes. Air fryer: bake at 320°F (160°C) for 45–50 minutes. Start checking after 40 minutes.
The loaf is ready when a toothpick inserted in the center comes out clean and the internal temperature reaches 200–205°F (93–96°C). Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.
Glaze and serve
Sift the powdered sugar into a bowl. Stir in the milk, a little at a time, until the glaze is thick but pourable. Drizzle half the white glaze over the cooled loaf.
1 cup (120g) powdered sugar (icing sugar), 1½–2 tbsp milk
Tint the remaining glaze with the matcha powder. Drizzle the matcha glaze over the loaf and let it drip down the sides.
½ tsp matcha powder
Notes
Dissolving the matcha in the buttermilk first is the key to smooth marbling – don't add the powder straight to the batter. The buttermilk also keeps both halves of the batter the same consistency, so they marble evenly instead of one sinking into the other.
Don't over-swirl. Two or three figure-eights are enough, as the batter keeps moving as it rises.
Air fryers vary, so start checking after 40 minutes. Make sure the pan fits in your air fryer and there's clear space above it. If the top browns too quickly in the air fryer, cover it with foil wrapped tightly around the rim of the pan or pinned down with air fryer magnets.
Storing and Freezing
Room temperature: keep the banana bread in an airtight tin for up to five days.
Freezer: freeze the loaf whole or in slices, unglazed, for up to three months. Slices can go straight into the toaster.
Color: the green fades a little over a few days, especially in bright light, so keep the loaf covered.