Preheat the air fryer. Set it to 325°F (160°C). Preheating helps the muffins rise right away and bake evenly.

Prep the cups. Place silicone muffin cups in the air fryer basket. If using paper liners, double them or lightly spray to prevent sticking. Plan for 6–8 muffins, depending on cup size.

Mix dry ingredients. In a medium bowl, whisk 1 1/2 cups flour, 2/3 cup sugar, 2 teaspoons baking powder, and 1/4 teaspoon salt. Remove 1 tablespoon of this mixture to toss with the blueberries later.

Combine wet ingredients. In another bowl, whisk 1 egg, 1/2 cup milk, 1/3 cup Greek yogurt, 1/4 cup oil (or melted butter), and 1 teaspoon vanilla. Add 1 teaspoon lemon zest if using.

Bring the batter together. Pour wet ingredients into the dry. Stir gently with a spatula until just combined. The batter should be thick and slightly lumpy. Do not overmix or the muffins can turn dense.

Fold in the blueberries. Toss 1 cup blueberries (fresh or frozen) with the reserved tablespoon of flour, then fold into the batter with a few gentle strokes. If using frozen, add straight from the freezer—no thawing needed.

Fill the cups. Divide the batter evenly among the muffin cups, filling each about 3/4 full. Sprinkle tops with a pinch of coarse sugar for a light crunch, if you like.

Air fry in batches. Place the basket back into the air fryer and cook at 325°F for 10–13 minutes. Do not overcrowd; leave space between cups for air flow. Work in batches if needed.

Check for doneness. Muffins are done when the tops are set and a toothpick comes out clean or with a few moist crumbs. If using large cups or lots of berries, you may need an extra 1–2 minutes.

Cool briefly. Let muffins sit in the cups for 5 minutes, then transfer to a rack. This helps them set and keeps the bottoms from steaming too much.

Serve warm. Enjoy as-is or with a pat of butter or a drizzle of honey. They’re best the day they’re made but keep well for a few days.