Sweet & Sour “Kielbasa” (adapted from Allrecipes)This recipe originally called for a slow cooker, which I don’t own. If you have one, use it! If you don’t, simmer over very low heat. 
5 Tbsp Butter1 large Onion, sliced3/4 Brown Sugar3 cups Ketchup4 Tbsp Apple Cider Vinegar1 1/2 tsp Spicy Brown Mustard1 Tbsp Worcestershire powder (the original recipe called for Worcestershire sauce, which contains anchovies)2 tsp Hot Sauce1 package Tofurky Kielbasa  (thanks to Jarrad for doing some Whole Foods kielbasa research for me)
Melt butter in a large saute pan over medium heat. Add onion and saute over low/medium heat until soft. Stir in ketchup, vinegar, sugar, mustard, hot sauce and Worcestershire. Simmer for about 20 minutes, stirring occasionally. Slice kielbasa into 1” pieces and add to saute pan. Mix with sauce and onions. Simmer over very low heat for 1 1/2 hours, stirring occasionally.