Use ripe, firm Roma, beefsteak, or round tomatoes. Remove stems and cores. Halve round tomatoes crosswise, plum tomatoes lengthwise. Scoop out seeds if desired to reduce moisture. Pat cut sides dry. Toss in a bowl with olive oil, salt, and black pepper, coating cut surfaces well. Add garlic and fresh herbs (thyme, basil, or oregano) if using. Line a large rimmed baking sheet with parchment or foil.

Preheat oven to 218°C. Arrange tomato halves cut-side up in a single layer on a baking sheet, leaving space between pieces. Pour any remaining seasoned oil over the tops. Roast on the middle rack for 20–35 minutes. Check at 20 minutes — small Roma halves may be done then, while larger beefsteak halves may need up to 35 minutes or slightly more. No flipping needed. Look for caramelized, tender tops as your doneness cue. For a deeply concentrated result, roast at 149°C for 45 minutes, then reduce to 121°C for 2–3 hours more, or go as low as 93°C for 6–8 hours.

At 218°C, tomatoes are done when skins are blistered and loosening, cut surfaces look caramelized and slightly shrunken, and edges show light browning. They should be soft and collapsed but still holding shape. Rest on the pan 5–10 minutes. Pour off and reserve the juices — great for sauces or bread dipping. Peel and discard loosened skins once cool enough to handle. Serve warm as a side, on bread, with pasta, or in salads. Refrigerate in an airtight container up to one week. Avoid overcrowding the pan, using underripe tomatoes, or pulling them before caramelization develops.