Red Onion Marmalade

1/4 cup olive oil
12 cups thinly sliced red onions (about 3 1/4 pounds)
1 tsp dried crushed red pepper
2 cup (packed) dark brown sugar
1 1/2 cup apple cider vinegar
1 cup dry Sherry
3 Tbsp grated peeled fresh ginger
1 cup raisins

Heat oil in heavy large pot over medium heat. Add onions and dried red pepper. Cover and cook until onions are tender, stirring occasionally, about 15 minutes.

Add brown sugar, vinegar, Sherry and ginger. Cook uncovered until onions are very tender and mixture is thick, stirring frequently, about 20 minutes.

Add raisins and cook until mixture is very thick and dark, stirring frequently, about 20 minutes. Season to taste with salt and pepper.

Ladle into prepared jars leaving 1/4” headspace. Process in a boiling water bath for 10 minutes. Adjust time according to altitude.

Makes: 5 half pints