In a medium bowl, toss the diced rhubarb with ½ cup white sugar. Set aside.

In a large mixing bowl, cream together the softened butter and remaining 1 cup of white sugar until light and fluffy. Beat in the egg and vanilla extract until well combined.

In a separate bowl, whisk together the flour, baking soda and salt.

Gradually add the dry ingredient to the creamed mixture, alternating with the buttermilk, until everything is incorporated.

Fold in the sugared rhubarb until evenly distributed throughout the batter.

Pour the batter into a greased and floured 9 x 13-inch baking pan and spread out evenly.

Bake at 350 degrees for 35-40 minutes, or until toothpick inserted into the center comes out clean. If using a smaller baking pan, bake for 30 minutes.

While cake is baking, prepare the butter sauce.

NOTE: If you don’t have buttermilk on hand, you can make it by adding 1 tablespoon of white vinegar to 1 cup of milk. **Let sit for 5 minutes**. Feel free to adjust the amount of sugar in the cake and sauce to suit your taste preferences. Cake can also be served with a dollop of whipped cream or scoop of vanilla ice cream instead of the butter sauce.