Select firm, crisp rhubarb stalks without blemishes for best flavor and color., Roast rhubarb until very soft for smooth blending and caramelized notes., Add water gradually during blending for a smooth puree., Adjust sweetness or tang by tasting and adding more brown sugar or vinegar as preferred., Start with a small amount of cayenne pepper and increase if more heat is desired., Use a wide, shallow pan for roasting to promote even browning without steaming., Variations include adding smoked paprika or chipotle for smokiness, maple syrup or honey for sweetness, apple cider vinegar for more tartness, adding roasted fruits for fruity twists, or Dijon mustard for extra tang., Store the sauce refrigerated in an airtight container for up to one month., Freeze in suitable containers or ice cube trays for up to three months; thaw in fridge before use., Water bath canning is possible: jars must be fully covered with at least 2 inches of water and boiled for 15 minutes; follow altitude-specific canning guides., Reheat gently on low heat to preserve flavor and texture., This sauce is vegan if Worcestershire sauce used is anchovy-free.