Preheat your oven to 350 degrees F and spray a 12 count muffin tin with non-stick spray or line with paper liners.
In a large bowl whisk together 2 cups of all-purpose flour, 1/2 teaspoon of baking powder, and 1/2 teaspoon of baking soda, set aside.
In a small mixing bowl whisk together 3/4 cup of granulated sugar, 1 large egg, 1/4 cup of plain Greek yogurt, 1/3 cup of vegetable oil, 1 cup of buttermilk, and 1 teaspoon of pure vanilla extract.
Add the wet ingredients to the dry and mix until just combined.
Fold the rhubarb into the batter.
Fill each muffin tin 2/3 of the way full of batter and top each muffin with 1 tablespoon streusel.
Bake for about 15-20 minutes or until a toothpick comes out clean when checked in the middle.
Let cool and enjoy within 3 days.
Add the brown sugar, flour and butter to the bowl of a food processor.
Pulse the mixture until the butter is combined and the texture of wet sand.
Remove the streusel from the food processor and top muffins.
