Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners.
In a large bowl, whisk together the flour, sugars, baking powder, baking soda, salt, and cinnamon.
In another bowl, beat the egg and mix in the oil, yogurt (or applesauce), and vanilla extract.
Pour the wet ingredients into the dry ingredients and stir until just combined.
Gently fold in the diced apples, ensuring they are evenly distributed.
Fill each muffin cup about 2/3 full with the batter.
Bake in the preheated oven for 20-25 minutes or until a toothpick comes out clean.
Remove from the oven and let cool in the tin for 5 minutes.
Transfer the muffins to a wire rack to cool completely.
Enjoy your delicious apple muffins warm or store them for later.