Cook The Potatoes In Their Jackets In 2 Cups Water Over Moderate Heat Until They Are Soft About 20 Minutes. Cool And Peel. Process To A Smooth Paste. Cook Together 1 Cup Water, Tomatoes, Scallions, Garlic, Bell Pepper, And Jalapeno Over Low Heat For 20 Minutes. Process To A Smooth Sauce And Strain Through A Metal Sieve To Remove Any Lumps. There Should Be About 2 Cups Sauce. Mix Together Into A Smooth Moist Paste, The Mashed Potatoes, Sauce, Margarine, Tortilla Flour, Salt, Allspice, Pepper And Dissolved Achiote. Mix Well. Put 3/4 Cup Of This Mixture Onto Foil And Fold Into A Rectangle. Pack Firmly When Folding. Steam The Tamale Over Moderate To High Heat For 30 Minutes. Serve Warm With A Liberal Squeeze Of Lemon.