Preheat your oven to 375°F (190°C) and line a muffin tin with paper liners.

In a mixing bowl, combine the flour, sugar, baking powder, and salt.

In another bowl, whisk together the melted butter, egg, milk, and orange zest.

Pour the wet ingredients into the dry ingredients and stir until just combined.

Gently fold in the chopped cranberries.

In a separate bowl, mix the brown sugar, flour, cinnamon, and melted butter to create the streusel topping.

Divide the muffin batter evenly among the prepared muffin tins, filling each about two-thirds full.

Sprinkle the streusel topping generously over each muffin.

Bake in the preheated oven for 20-25 minutes or until a toothpick inserted in the center comes out clean.

Allow the muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.