An oven-roasted, highly flavorful tomato concentrate, it trumps any store-bought tomato paste you've ever tasted. This is adapted from Molly Watson's blog The Dinner Files. She adapted her recipe from Paul Bertolli's book, Cooking by Hand. —Marisa McClellan
Chop tomatoes into quarters. Combine them in a large pan with 1/4 cup olive oil and bring to a simmer. Cook until they are soft and the peels begin to detach from the tomato flesh.
Push warm tomatoes through a food mill, sieve or chinois, so that you separate the tomato pulp from the seeds and skins.
Divide the tomato pulp between two large, rimmed baking sheets (I used two half sheet pans).
Place baking sheets in the oven and bake at 350° F. Check tomatoes every half hour, stirring the paste and switching the position of the baking sheets so that they reduce evenly.
Over time, the conserva will start to reduce to the point where it doesn’t fill the baking sheet any more. At this point, I combine the contents of the two pans into and continue to bake.
When the conserva is shiny, brick-colored and has reduced by more than half, it is done. There shouldn’t be any remaining water or moisture separating from the paste at this point.
Scrape finished conserva into clean half or quarter pint jars. Top with a layer of olive oil and place in either the refrigerator or the freezer. As long as you keep it well-covered with olive oil and ensure that you only use a very clean spoon to remove it from the jar, it will keep in the fridge for a month or so. Frozen, it will keep for up to nine months.