A light and airy muffins filled with tart rhubarb and topped with a sweet-spicy streusel.
Preheat oven to 350. Line muffin tin with paper cups. Set aside. Combine flour, baking soda, baking powder and salt in a medium mixing bowl. In a separate bowl, combine butter, brown sugar and egg. Whisk until smooth. Pour in buttermilk and vanilla. Whisk until just combined. Add in the dry ingredients and mix until combined. Do not over-mix. Fold in rhubarb. Spoon batter into paper cups-filling almost to the top. Meanwhile, combine melted butter, sugar, cinnamon and nutmeg. Spoon over tops of muffins. Bake for 25 minutes or until a toothpick inserted comes out clean.