Prep your pan and oven: Heat the oven to 350°F (175°C). Line a 12-cup muffin pan with paper liners or grease lightly.
Mix dry ingredients: In a large bowl, whisk flour, protein powder, baking powder, baking soda, and salt until evenly combined.
Whisk wet ingredients: In a separate bowl, whisk eggs, Greek yogurt, oil, milk, sugar, honey or maple (if using), lemon zest, lemon juice, and vanilla until smooth and creamy.
Combine gently: Pour the wet mixture into the dry ingredients. Stir with a spatula just until no big streaks of flour remain. The batter will be thick; avoid overmixing.
Prepare blueberries: Toss blueberries with 1 tablespoon flour to help prevent sinking. Fold them into the batter with a few gentle turns.
Fill the cups: Divide the batter evenly among the muffin cups, filling them nearly to the top. Sprinkle with coarse sugar if you like a bit of crunch.
Bake: Bake for 18–22 minutes, or until the tops are set and a toothpick comes out clean or with a few moist crumbs. If using frozen berries, add 1–2 minutes.
Cool: Let the muffins rest in the pan for 5 minutes, then transfer to a wire rack. Cool at least 10–15 minutes before eating so the crumb sets.
Enjoy: Serve warm or at room temperature. Pair with a swipe of almond butter for extra staying power.