Preheat your oven to 425°F (220°C) and line two muffin tins with paper liners.

In a large bowl, combine the chopped peaches, dark brown sugar, optional ground cinnamon, melted salted butter, and vanilla extract. Stir gently.

While the peach mixture bakes, whisk melted butter, brown sugar, Greek yogurt, and eggs in another bowl until smooth.

Gently fold in the all-purpose flour, baking powder, and salt until just combined.

Carefully take the muffin cups out of the oven and fill each cup with the muffin batter all the way to the top.

Bake at 425°F (220°C) for the first 8 minutes, then reduce the temperature to 350°F (175°C) and bake for an additional 20-30 minutes.

Allow the muffins to cool in the tins for about 5 minutes before removing.