Instructions:
- Preheat oven to 400°F (200°C). Line a standard 12-cup muffin tin with paper or silicone liners or grease thoroughly.
- In a large bowl, whisk together the flour, sugar, baking powder, and salt until thoroughly combined.
- In a medium bowl, gently whisk the eggs until just broken up. Add the cottage cheese, milk, oil, vanilla extract, and lemon zest (if using). Whisk until mostly smooth; a few small lumps of cottage cheese are acceptable.
- Pour the wet mixture into the dry ingredients. Using a rubber spatula, fold just until no dry streaks of flour remain. Do not overmix; lumps are essential for tenderness.
- Gently fold in the blueberries. If using frozen berries, toss them with one teaspoon of flour before adding them to the batter.
- Divide the batter evenly among the 12 cups, filling them nearly to the top to encourage domed tops.
- Bake for 5 minutes at 400°F (200°C). Then, reduce the oven temperature to 375°F (190°C) (without opening the door if possible) and continue baking for another 15–19 minutes, or until a toothpick inserted into the center comes out clean.
- Let the muffins cool in the tin for 5 minutes before transferring them immediately to a wire rack to cool completely.