Preheat and prep: Heat the oven to 375°F (190°C).
Line a 12-cup muffin pan with paper liners or lightly grease each cup.
Mix dry ingredients: In a large bowl, whisk flour, protein powder, baking powder, baking soda, salt, and cinnamon until evenly combined. This helps prevent clumps.
Whisk wet ingredients: In a separate bowl, whisk maple syrup, brown sugar, eggs, Greek yogurt, milk, oil, and vanilla until smooth and glossy.
Combine gently: Pour the wet mixture into the dry ingredients. Stir with a spatula until just combined.
A few small streaks of flour are fine. Do not overmix or the muffins will be tough.
Fold in pecans: Add chopped pecans and fold gently. Save a few for topping.
Fill the pan: Divide the batter evenly among the muffin cups, filling each about 3/4 full. Sprinkle with extra pecans and, if using, a little turbinado sugar.
Bake: Bake for 16–20 minutes, or until the tops are set and a toothpick comes out with a few moist crumbs.
If your oven runs hot, start checking at 15 minutes.
Cool: Let muffins cool in the pan for 5 minutes, then transfer to a wire rack. Enjoy warm or at room temperature.