1Heat the oven to 325°F and arrange the rack in the middle.
2Slice 1/8 inch off both the top and bottom of the tomatoes. Stand each tomato on one end and slice downward, following the curve and cutting just into the flesh, leaving behind the seeds (the pieces you cut off will resemble petals). Discard seeds and pulpy portion.
3Combine the tomato petals with remaining ingredients in a medium bowl and toss to coat. Spread the tomato petals, cut side down, on a baking sheet spaced about 1/2 inch apart. Pour remaining contents of the bowl over tomatoes.
4Roast the tomatoes until they’re shriveled and dark red but still hold their shape, about 45 to 50 minutes. Cool in the pan, then transfer to a container with a tightfitting lid and cover with any remaining oil from the baking sheet (add additional oil if there’s not enough to cover the tomatoes). Store in the refrigerator until ready to use.