Created by Cheesehead on November 24, 2011
Step 1: Halve onions lengthwise and cut into thin slices. Heat butter in large heavy skillet set over medium heat.
Step 2: When melted and hot, add onions and sugar and stir occasionally until onions are soft and start to caramelize, 10 to 15 minute. Add wine and 1/4 cup vinegar and stir until mixture almost comes to a boil. Reduce heat and simmer until liquids have evaporated and onion is shiny, 15 to 20 minutes.
Step 3: Remove from heat and sprinkle in salt, adding more if needed. For tarter taste, stir in another 2 to 3 teaspoons vinegar.
Step 4: The marmalade can be prepared 5 days ahead; cover and refrigerate. Reheat, stirring, just to warm before using. Makes about 1 1/2 cups.