From the I Love New York cookbook by Daniel Humm and Will Guidara
Note: The original recipe calls for 8 large beefsteak tomatoes in order to produce about 5 cups of roasted purée. I filled two sheet pans with about 9 1/2 pounds of both beefsteak and cherry tomatoes, and I got about 14 cups of purée. Roast as many tomatoes as you wish, but you will need at least 3 pounds for this recipe. The extra juice freezes well.
Reducing: After the tomatoes are roasted and passed through a food mill, they will be reduced with sugar and vinegar until the mixture is about 3 1/2 cups. You can eye this—as long as the mixture is thick and looking somewhat like ketchup, it will be fine—or you can do this trick before you start cooking: Fill whatever pot you are going to use with 3 1/2 cups water; take a skewer or chopstick and dip it into the water; mark where the water hits the skewer/chopstick with a marker or a rubber band. Once you have this stick marked, you can dip it into the reducing tomato mixture to gauge how it is doing. —Alexandra Stafford
3 to 5 pounds
tomatoes, cherry, beefsteak, plum (see headnote)
Preheat oven to 450° F. Core and quarter the tomatoes and toss with 2 tablespoons of the oil. Place the tomatoes on a rimmed baking sheet lined with parchment paper. Roast in the oven until tender, about 15 minutes.
Pass the tomatoes through a food mill. This should yield about 5 cups of purée. If you have leftover purée, freeze it—it makes a very nice Bloody Mary. In a large straight-sided pot, heat 2 tablespoons of canola oil over medium-low heat. Add the onion and garlic, and sweat until tender, about 5 minutes. Add the tomato purée, brown sugar, and cider vinegar. Raise the heat to medium-high to high, stirring frequently to avoid burning, and reduce the mixture to 3 1/2 cups, or until thick and coating the back of a spoon. You can also simmer this slowly over medium to medium-low heat—this may take as long as an hour. (See headnote above in regards to reducing.)
Transfer to a blender or food processor and blend on high while streaming in the remaining canola oil. Pass through a chinois (optional) and season with the vinegar and salt to taste, starting with 1 tablespoon vinegar and 1 tablespoon salt.
Transfer to a glass jar, cover, and keep in the refrigerator for up to 1 week.