Preheat the oven to 400°F. Place paper liners in a 12-well muffin tin. Coat the liners with cooking spray. Make the streusel topping: Combine flour, pecans, brown sugar, cinnamon, and melted butter in a medium bowl. Use your fingers to press the mixture into large clumps, if desired.
Make the muffins: Toss 1 tablespoon of the flour with the blueberries and set aside. Stir together the remaining flour and baking powder in a small bowl.
Whisk together the milk, oil, granulated sugar, mayonnaise, lemon zest, egg, and vanilla in a large bowl until combined. Add the flour mixture and stir until the batter is smooth. Add the blueberries and gently fold to combine.
Divide the batter evenly among the muffin liners and sprinkle with the streusel topping. Bake the muffins at 400°F for 20 to 23 minutes, until the tops are golden brown and a toothpick inserted in the center comes out clean. Let the muffins cool in the pan for 5 minutes before removing from the tin to a wire rack to cool.