Preheat the oven to 400°F and position a rack in the center; line a 12-cup muffin pan with paper liners or lightly grease the cups.

In a medium bowl whisk together 2 cups all-purpose flour, 1/2 cup granulated sugar, 2 teaspoons baking powder, 1/2 teaspoon baking soda, and 1/2 teaspoon kosher salt until combined.

In a large bowl whisk 3/4 cup plain yogurt, 1/3 cup milk, 2 large eggs, 6 tablespoons melted butter (warm, not hot), 1 teaspoon vanilla, and 1 teaspoon lemon zest if using until smooth.

Pour the dry ingredients into the wet and fold gently with a rubber spatula until most flour streaks disappear; do not overmix—the batter should be lumpy.

Place 1 cup blueberries in a small bowl and toss with the reserved 1 tablespoon of flour, then fold the berries into the batter gently until evenly distributed.

Scoop batter into the prepared muffin cups using a 1/4-cup scoop, filling nearly full. For the crumb topping, rub together 1/3 cup flour, 3 tablespoons brown sugar, 2 tablespoons cold butter, and a pinch of salt until coarse crumbs form and sprinkle over the muffins.

Bake at 400°F for 5 minutes, then reduce oven temperature to 375°F and continue baking for 12–16 minutes until tops are golden and a toothpick inserted into the center comes out with a few moist crumbs.

Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool another 10–15 minutes before serving.