Preheat oven to 350°F and add muffin liners to 24 muffin cups.
In a large bowl, stir together the sugar, brown sugar, oil, buttermilk, egg and vanilla.
Next, add the flour and baking soda and stir until just combined.
Add the rhubarb and stir until well dispersed throughout the batter; set aside.
Next, add the topping ingredients in a small bowl and use a fork to mix until combined.
Fill each muffin cup 2/3 full and top each muffin with about 1 tsp topping.
Bake for 18-22 minutes and remove from the muffin tin to cool.