1. Preheat the oven to 375°F and line a 12-cup muffin pan with paper liners or lightly grease each cup.

2. Rinse the rhubarb, trim the ends, discard the leaves, and cut the stalks into 1/2 inch pieces. Pat dry with a clean towel.

3. In a large bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, granulated sugar, and brown sugar until evenly combined.

4. In a separate bowl or large measuring jug, whisk the oil, buttermilk, eggs, and vanilla until smooth.

5. Pour the wet mixture into the dry ingredients and stir gently just until no dry streaks of flour remain.

6. Fold in the chopped rhubarb until the pieces are evenly distributed through the batter.

7. For the crumb topping, rub the flour, sugar, butter, and cinnamon together with your fingertips until coarse crumbs form.

8. Divide the batter between the 12 muffin cups, filling each about two-thirds full, and mound slightly for high domes if desired.

9. Sprinkle the crumb topping evenly over each muffin.

10. Bake for 18 to 22 minutes, or until the tops are golden and a toothpick inserted in the center comes out with just a few moist crumbs.

11. Cool in the pan for 5 minutes, then transfer muffins to a wire rack to cool completely.

12. Serve warm or at room temperature. Store leftovers airtight or freeze for longer storage.