1 Put Half Of The Chopped Rhubarb, Lemon Juice, Lemon Zest, Rosemary, Sugar, Salt And 2 Cups Of Water Into A Medium Saucepan. Bring To A Boil. Reduce To A Simmer And Cook, Uncovered, For 15 Minutes. Strain And Discard Solids. 2 Return Strained Liquid To Pan. Add The Remaining Rhubarb To The Pan And Cook For 2 Minutes, On Medium, With Minimal Stirring. 3 Put 1 Cup Of Chilled Water Into A Small Bowl. Sprinkle Gelatin Over The Water To Soften The Gelatin. Let Sit For 1 Minute. Stir The Softened Gelatin Mixture Into The Rhubarb Rosemary Mixture. Let The Mixture Cool Until It Is Slightly Warm, No Longer Hot, To The Touch. 4 Pour Rhubarb Mixture Into A Mold (Can Use A Loaf Pan). Stir In The Chopped Cucumber. Chill In The Refrigerator 4 To 5 Hours, Until Set Firm. The Top Should Feel Dry, Not Sticky. (If You Want The Cucumber Better Distributed Through The Salad, Stir It In Only After The Salad Has Chilled A While And Begun To Set.) 5 To Unmold, Fill A Basin Or A Large Bowl With Warm Water. Lower The Bottom Of The Mold Into The Water. Count 10 Seconds And Remove. Use A Blunt Knife To Loosen The Gelatin From The Sides Of The Mold And Break The Vacuum. Place A Plate Upside Down On Top Of The Mold And Then Carefully Turn The Mold Over, Holding On To The Plate. Gently Lift Off The Mold. If The Salad Sticks To The Mold, Place It In The Warm Water For A Few Seconds More.