Rhubarb Cake with Streusel Topping and Vanilla Butter Sauce

2 tablespoons butter (no substitutes), softened
1 cup granulated sugar
1 egg
2 cups all-purpose flour
1 teaspoon baking powder
1/2 teaspoon baking soda
1/2 teaspoon salt
1 cup buttermilk
2 cups chopped fresh or frozen rhubarb, thawed

Streusel Topping
1/4 cup all-purpose flour
1/4 cup granulated sugar
2 tablespoons butter (no substitutes)

Vanilla Butter Sauce
3 tablespoons butter (no substitutes)
1/4 cup plus 2 tablespoons granulated sugar
1/4 cup plus 2 tablespoons evaporated milk
1 teaspoon pure vanilla extract

In a mixing bowl, cream butter and sugar. Beat in egg.

Combine flour, baking powder, baking soda and salt. Add to creamed mixture alternately with buttermilk, beating just until moist. Fold in the rhubarb.

Pour into a greased 9-inch square baking dish.

Combine topping ingredients; sprinkle over batter.

Bake at 350 degrees F for 40 to 45 minutes or until a wooden pick comes out clean and the cake is lightly golden brown.

For sauce, melt butter, sugar and milk in a small saucepan over about medium heat. Bring to a boil; cook and stir for 2 to 3 minutes or until slightly thickened. Remove from heat and stir in vanilla extract.

Serve the warm sauce over slices of warm cake.

Serves 8-10.