Urgent! A question about a recipe: Sweet & Savory Tomato Jam

I have a question about step 1 on the recipe "Sweet & Savory Tomato Jam" from Jennifer Perillo. It says:

"Put all ingredients in a 2-quart pot. Bring to a gentle boil, then reduce heat to a simmer. Cook until thickened to a jam-like consistency, about 3 hours. Transfer to sterilized glass jars and store in refrigerator for up to two weeks, or use a hot-water canning bath for 15 minutes for long-term storage." Cook covered or uncovered?