Cut the unpeeled pears into 1-inch pieces without removing the cores. (The core and peel are loaded with pectin, which will help set up the preserves, and rich in flavor.) Place in a heavy, large saucepan. Add the wine, water and lemon juice. Bring to a boil. Cover and simmer until the pears are soft, pushing down into the liquid occasionally, 20-30 minutes.
Preheat the oven to 300℉. Set a food mill over a large bowl. Pour or spoon the pear mixture into the mill in batches and force through the food mill to remove peels and cores.
Transfer the pear puree to a food processor, in batches if necessary. Puree until silky smooth.
Pour the pear puree into a 13x9" glass baking dish. Add the white sugar, brown sugar, lemon slice, cinnamon stick if using, vanilla bean, cardamom and salt. Stir until the sugar dissolves. Roast until the spread thickens, stirring every 30 minutes or so, for about 2 hours. To test for doneness, spoon a small amount onto a plate. It should set up almost immediately with no spreading or wateriness. Continue cooking if it's not ready.
Meanwhile, wash 5 8-ounce canning jars or 3 12-ounce jars and 1-8-ounce jar, and jar lidsIf you plan on preserving for long keeping, bring a canning pot two-thirds full of water to a boil. Submerge the jars in the hot water, cover and boil for 10 minutes. Wash the lids, place in a small saucepan and bring to a simmer; turn off the heat but keep warm. When ready to can, bring a kettle of water to a boil and set aside. Remove the jars from the boiling water and invert onto paper towels to drain. Let the lids dry on another paper towel. One at a time, spoon the pear butter into hot jars, leaving ¼" space on the top. Tap gently on the work surface. Wipe the top edge clean with a damp paper towel. Place a dry lid atop the jar. Screw a band on the jar just until secure, but not tightly. Repeat with the remaining pear butter and jars. Jars can be cooled and stored in the refrigerator for about 2 months.
For longer keeping, submerge the jars in the canning pot. Add enough boiling water to cover by at least 1". Cover and boil for 10 minutes. Transfer the jars to a rack and cool. To test the seal, press on the center of the lid, it should be taut and slightly indented. If not, refrigerate for up to 2 months. If the seal is tight, store the jar in a cool, dark area for up to 1 year.