Preheat the oven 350℉. Lightly spray a muffin pan and set aside.
In a large bowl, mix together the flour, baking powder, baking soda, salt and 1 teaspoon ground cinnamon.
In a separate bowl, mix together the eggs, yogurt, brown sugar, oil and vanilla until smooth.
Slowly mix the dry ingredients into the wet ingredients until just combined.
Divide the batter into the prepared muffin pan and bake in the preheated oven for around 15 minutes, or until a toothpick inserted into the center of a muffin comes out clean. Allow to cool in the pan for around 5 minutes before transferring to wire racks to cool completely.
In a small bowl, combine the sugar and cinnamon. Dip each muffin into the melted butter, then dip in the cinnamon sugar.
Notes
Use a silicone muffin pan for easy muffin removal. I love this silicone muffin pan.
To divide the batter easier, use a large cookie scoop. I use this scoop to avoid mess.
Don't overmix the batter. Mix the dry and wet ingredients until just combined to ensure that the muffins don't end up too dense.
Freezing: If you wanted to freeze these muffins, do so before dipping in butter and cinnamon sugar. They can be stored in a large freezer bag for up to 3 months. When ready to eat, thaw at room temperature before dipping in melted butter and cinnamon sugar.