Heat oil in a large nonstick skillet over medium-high heat. Add bell pepper, shallots, jalapeño pepper, and garlic; sauté 2 minutes. Cover, reduce heat, and simmer 10 minutes or until tender. Add broth; simmer, uncovered, 15 minutes or until liquid almost evaporates.
Place pepper mixture in a blender, and process until smooth. Strain purée through a sieve over a bowl; discard solids. Stir in vinegar and salt.
One of my favorite recipes, I make this one all the time just as it is, and serve it with any kind of fish. I usually make extra and freeze some for when I'm rushed for dinner.