- Melt butter gently.
- Meanwhile, mix sugar, baking soda, and flour.
- Add butter and crumble.
- Divide in half and press ½ out to line bottom of 9 inch square pan.
- Combine ingredients, except rhubarb.
- When mixed, pour over rhubarb and toss to coat well.
- Place in pan with crumb crust and sprinkle remaining crust on top.
- Bake 1 hour in preheated 350 °F oven.
- Sprinkle with confectioners' sugar and cut in squares and serve.
- May be served with ice cream.