Heat oil in a medium skillet over medium heat until shimmering. Add onions and salt, and cook until softened and just translucent but not brown, 8 to 10 minutes, stirring occasionally.

Add in pepper, wine, sugar, honey, thyme and vinegar. Bring to a boil, then reduce heat low, and let simmer until liquid thickens, becomes syrupy and is mostly reduced, about 40 to 50 minutes. Stir occasionally. Season with additional salt and pepper to taste. Allow jam to cool, then serve or store in an airtight container in the refrigerator for up to 2 weeks. (Let onion jam return to room temperature before using).