Wash and dice the rhubarb into ½ inch pieces. Cut them into even pieces so they will cook evenly.
In a medium saucepan, add the diced rhubarb, 1 cup white sugar, and water. Cook over medium-low heat for 6-8 minutes until tender. Stir several times.
In a large mixing bowl, add the remaining sugar (½ cup) and softened butter. Cream together with a hand mixer or a stand mixer. Add the egg and vanilla. Mix until combined.
Next, add the flour, baking powder, and salt to the creamed butter mixture. Stir until combined. Pour in the milk, stir again.
Lightly grease an 8x8-inch or 9x9-inch baking dish with nonstick cooking spray or softened butter.
Pour the cake batter into the prepared pan.
Next, gently pour the cooked rhubarb sauce over the cake batter.
Bake in a preheated 350 degree F oven for 45-50 minutes or until the top of the cake turns golden brown.
Remove from the oven and allow the cake to cool. This will help thicken the pudding sauce.
Serve with fresh whipped cream or a scoop of vanilla ice cream.
Notes
Note 1: For gluten free use Bob’s Red Mill 1-to-1 gluten free flour. Both flour options have been tested and have been successful. Note 2: Use lactose free milk if needed. Unsweetened almond milk will also work.