Preheat your oven to 375℉ / 190℃. Line a 12 hole muffin pan with paper liners.
Prepare the apples. Peel if desired, and dice them finely.
2 cups (200 g) apple
Combine the flour, baking powder, baking soda, salt, and cinnamon in a mixing bowl.
2 cups (240 g) all-purpose flour, 1 ½ teaspoons baking powder, ¾ teaspoon baking soda, ½ teaspoon salt, 1 ½ teaspoons ground cinnamon
Mix almond or soy milk and vinegar in a jug to make the vegan buttermilk. Set aside to curdle and thicken slightly.
2 teaspoons apple cider vinegar, 1 cup (240 ml) almond milk or soy milk
Stir together the brown sugar and vegetable oil in a large mixing bowl.
⅔ cup (140 g) dark brown sugar, ¼ cup + 2 tablespoons (90 ml) vegetable oil
Add the vegan buttermilk and stir until well combined.
Gently mix in the flour mixture using a silicone spatula, until the batter is barely combined (don't overwork it).
Add the diced apple and fold it into the batter. If desired, reserve some pieces of apple to sprinkle on top of the muffins before baking.
Scoop the batter into the muffin liners. Take care not to overfill and leave at least ½ inch or 1cm space beneath the top.
Bake for 20-25 minutes and test that a skewer inserted into the center of a muffin comes out clean without any uncooked batter.
Cool the muffins on a wire rack for 30 minutes and then enjoy!