Heat the oven to 350°F (175°C). Line a 12-cup muffin tin with paper liners, or grease each cup thoroughly so the muffins release easily after baking.

Prepare the crumb topping first by stirring together the flour, packed light brown sugar, and cinnamon in a medium bowl. Add the melted unsalted butter and mix until coarse, irregular crumbs form, then set the topping aside.

In a large bowl, whisk together the flour, granulated sugar, baking powder, salt, and cinnamon. Mixing the dry ingredients evenly helps distribute the leavening and spice throughout the batter.

In a separate bowl, whisk the eggs, milk, neutral vegetable oil, and vanilla extract until blended. The wet mixture should look smooth before it is added to the flour mixture.

Pour the wet ingredients into the dry ingredients and stir just until combined. Stop while a few small lumps remain, because excessive stirring can make the finished muffins dense and tough.

Divide the batter evenly among the prepared muffin cups, filling each about two-thirds full. A spoon or cookie scoop makes portioning easier and helps the batch bake at the same rate.

Sprinkle the crumb topping generously over each portion of batter, gently breaking apart any crumbs that are larger than you prefer. Cover the surface well so every muffin receives a buttery cinnamon topping.

Bake for 20 to 25 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out clean. Begin checking at 20 minutes, since oven performance and muffin-tin material can affect the final baking time.

Cool the muffins in the pan for about 5 minutes, then transfer them to a wire rack. Letting them cool briefly allows the crumb topping to set while keeping the centers soft and pleasant to eat.