Preheat your oven to 425°F (218°C). Arrange the peppers on a baking sheet and roast for about 40 minutes, turning halfway through.

Once roasted, remove from oven and let cool. Peel off the skins, slice open to remove seeds.

In a food processor, combine peeled peppers and garlic. Pulse until roughly chopped.

Transfer the mixture to a saucepan. Add olive oil, vinegar, and salt. Simmer for 30 minutes until thickened.

Allow to cool, transfer to a clean container, and refrigerate until ready to use.