2 C all-purpose flour
3/4 C sugar
2 1/2 tsp baking powder
1 tsp ground cinnamon
1/2 tsp baking soda
1/2 tsp kosher salt
1 C sour cream
8 Tbsp unsalted butter, melted and cooled slightly
2 large eggs
1 tsp pure vanilla extract
1 1/2 C 1/4 inch diced rhubarb
3 Tbsp granulated sugar
1/2 tsp ground cinnamon
Preheat oven to 400 F degrees. Move rack to center position of oven. Line a muffin tin with paper or foil liners.
In a large mixing bowl, combine flour, sugar, baking powder, cinnamon, baking soda, and salt. Whisk to blend.
In a medium bowl, whisk sour cream, butter, eggs, and vanilla until smooth.
Stir sour cream mixture into dry ingredients until batter just comes together. Do not overmix. Stir in rhubarb. The batter will be thick.
Divide batter among muffin cups. The batter should mound a bit higher than the tops of the cups.
In a small bowl, combine sugar and cinnamon. Mix well. Sprinkle 1/2 tsp of cinnamon mixture over each muffin.
Bake for 18 to 22 minutes, or until golden brown, and a toothpick inserted in the center comes out clean.
Cool in pan for 5 to 10 minutes before removing from pan. Cool on a wire rack slightly before serving.