This charred tomato relish is a quick, chunky condiment built around broiled heirloom tomatoes, red onion, garlic, and fresh basil. It comes together in 35 minutes and costs almost nothing to make. The honest reason to make it: it turns a plain grilled burger into something that actually tastes finished.
What makes this version work
Two things matter here. First, leaving the tomatoes skin-side up under the broiler until the skins genuinely blacken — not just blister — pulls out a deep, slightly bitter char that balances the tomatoes’ natural sweetness once the skins are peeled away. Pull them too early and you get roasted tomatoes, which is fine but not the same thing. Second, adding the balsamic vinegar directly into the skillet with the tomatoes and letting it cook down for a full five minutes concentrates the acid and rounds out any sharpness. Skip that cook time and the vinegar tastes raw against the smoky tomatoes. Get both of those right and the relish holds its own on a burger without getting lost under the patty.
Troubleshooting
- Relish is watery and won’t hold on the bun: Heirloom tomatoes release a lot of liquid. After chopping the peeled tomatoes, let them drain in a colander for 5 minutes before adding them to the skillet. This alone fixes most runny batches.
- Skins won’t peel cleanly after broiling: Transfer the hot tomatoes directly into a bowl and cover tightly with plastic wrap for 5 minutes. The trapped steam loosens the skins so they slip off in one piece instead of tearing.
- Garlic tastes sharp or raw in the finished relish: Your heat was too high or the sauté time too short. Garlic needs the full 5 minutes over medium — not medium-high — to mellow properly. If it starts to brown before the onion is translucent, add a tablespoon of water to the pan.
- No heirloom tomatoes available: Roma tomatoes work well because they’re meatier and less watery than standard round tomatoes. Avoid beefsteak varieties here — too much liquid, not enough flavor payoff after charring. Canned whole San Marzanos, drained and halved, are a solid off-season substitute; broil them the same way.
- Basil has wilted or you don’t have any: Fresh flat-leaf parsley stirred in at the end gives a similar brightness without the sweetness. Dried basil added during cooking is not a good swap — it turns dusty and bitter in this recipe.
Storage and reheating
Store the cooled relish in a sealed jar or airtight container in the fridge for up to 5 days. The flavor actually improves after 24 hours once the garlic and balsamic settle in. For longer storage, freeze it in small portions — an ice cube tray works well — for up to 2 months; thaw overnight in the fridge. To reheat, warm it gently in a small saucepan over low heat, stirring occasionally. Microwaving works in a pinch but tends to make it watery; if that happens, let it simmer in a pan for a minute to tighten back up. Add the fresh basil after reheating, not before freezing.
Charred Tomato Relish
Ingredients
- 2 cups organic heirloom tomatoes halved
- 1 medium red onion chopped
- 2 cloves garlic minced
- 1 tablespoon olive oil
- 1 tablespoon balsamic vinegar
- 1 teaspoon sea salt to taste
- ½ teaspoon ground black pepper
- ¼ cup fresh basil leaves chopped
Instructions
- Preheat your grill or broiler to high. Arrange the tomato halves, skin-side up, on a baking tray.
- Grill or broil the tomatoes for 8-10 minutes until the skins are charred and blackened. Allow to cool slightly before removing the skins.
- In a skillet over medium heat, warm the olive oil and sauté the red onion and garlic until translucent and fragrant, about 5 minutes.
- Coarsely chop the skinned tomatoes and add them to the skillet. Stir in the balsamic vinegar, sea salt, and black pepper.
- Cook the mixture for an additional 5 minutes, allowing the flavors to meld. Lastly, incorporate the fresh basil just before serving.
Notes
Nutrition
Common questions
Can I use regular tomatoes instead of heirloom?
Yes — Roma tomatoes are the best everyday substitute because they’re dense and low in water. Standard round tomatoes can work but they release a lot of liquid during cooking, which makes the relish harder to thicken without a longer cook time.
What can I use instead of balsamic vinegar?
Red wine vinegar is the closest swap and works well at the same quantity. Sherry vinegar (as noted in the recipe card) is also good; apple cider vinegar is a little sharper but still fine — use about three-quarters of a tablespoon and taste as you go.
Can I make this without a grill or broiler?
A dry cast-iron skillet over high heat is the best alternative. Place the tomato halves cut-side down first for 3–4 minutes to get some caramelization, then flip skin-side down and press lightly until the skins blister and darken. It won’t char quite as evenly as a broiler but gets close.
How much relish does one batch actually make?
Roughly 1 to 1.5 cups after cooking down, which is enough to top 4 burgers generously. Two cups of raw heirloom tomatoes loses significant volume once charred, peeled, and simmered, so double the batch if you’re feeding more than four people or want leftovers.
What to cook next
- BBQ Cheeseburger Recipe
- Halloumi King Burger Homage
- Ultimate Guacamole Bacon Burger
- Veggie Sauce Burger Perfection