Preheat oven to 400 degrees Fahrenheit. Grease or line a 12-cup muffin tin.

In a small bowl, stir together all streusel ingredients until mixture is crumbly. Set aside.

In a separate bowl, combine diced rhubarb and 1/3 cup sugar. Set aside.

In a large bowl, blend together flour, 3/4 cup sugar, baking powder and salt. Drain rhubarb and stir into flour mixture.

In a separate medium bowl, whisk together liquid ingredients; gently stir into the flour-rhubarb mixture until just combined.

Divide evenly among muffin cups and top with streusel mixture.

Bake 20 to 25 minutes or until light brown and toothpick inserted in the center comes out clean. Serve warm or at room temperature.