1 jalapeño, chopped (remove stems and seeds for less heat)
1 tablespoon butter
1 1/4 pounds garden tomatoes roughly chopped
1/2 cup white sugar
1/4 cup light brown sugar
4 tablespoon apple cider vinegar
1 teaspoon kosher salt
1/2 teaspoon red pepper flakes
DIRECTIONS
Melt butter in a large heavy-bottomed stainless steel or cast iron saucepan over high heat. Add onions, jalapeños and cook, stirring frequently, until bottom of pan is glazed in a pale brown fond, about 5 minutes. Add 2 tablespoons water and scrape up fond with wooden spoon. Continue to cook, stirring frequently, until fond has built up again, about 2 minutes longer. Add 2 more tablespoons water and scrape up browned bits. Repeat cooking, adding water, and scraping until onions are completely softened and a deep, dark brown, about 15 minutes total.
Add tomatoes, white sugar, brown sugar, vinegar, salt, and red pepper flakes in with the onions; stir to combine. Bring mixture to a boil, then reduce heat and simmer, stirring occasionally, until tomatoes have broken down and jam has thickened and developed a jammy consistency, 2 to 2 1/2 hours. Remove from heat, let cool. Transfer jam to a an airtight container and store in refrigerator for up to two weeks.
This is a recipe I found in 2011 from Real Simple and thought sounded fantastic. I finally got around to making it and it was incredibly easy and tasted wonderful too.