Combine: rhubarb, flour, sugar, orange zest and salt.
Spread in a greased 9x13" pan.
Sprinkle with topping mix of: butter, flour, brown sugar, rolled oats, salt, chopped nuts.
(this recipe makes way more topping than you will need even if you like lots of topping! It freezes well for use on lots of other things too)
Bake at 350°F for about 40 minutes or till golden brown and bubbly in the middle.