Step 1

Season the beef with kosher salt and transfer to a large plate. Refrigerate, uncovered, for at least 12 hours or up to 24 hours. Bring to room temperature before cooking.

Step 2

Meanwhile, in a large colander, toss the tomatoes with 1 teaspoon of kosher salt and let stand for 30 minutes. In a medium saucepan, bring the vinegar, sugar, 1 tablespoon of kosher salt and 3 cups of water to a boil, stirring to dissolve. Add half of the tomatoes and simmer over moderately low heat until they start to soften, about 3 minutes. Using a slotted spoon, spread them on a large rimmed baking sheet to cool. Repeat with the remaining tomatoes. Discard the brine; wipe out the saucepan.

Step 3

In the medium saucepan, heat the olive oil. Add the garlic and cook over moderate heat until fragrant but not browned, about 1 minute. Remove from the heat. In a large bowl or two 1-quart heatproof jars, layer the tomatoes with the olive oil, garlic, mint and crushed red pepper. Let cool completely, then refrigerate. Bring to room temperature before serving

Step 4

Preheat the oven to 225°. Pat the beef dry with paper towels. In a large skillet, heat the canola oil. Cook the beef over moderate heat, turning, until browned all over, about 8 minutes. Set a rack in a small roasting pan and place the beef on it. Transfer to the oven and roast for 1 1/2 to 2 hours, until an instant-read thermometer inserted into the center of the meat registers 120° for medium-rare. Transfer the beef to a cutting board and tent with foil. Let rest for 30 minutes.

Step 5

Discard the string and thinly slice the roast beef against the grain; transfer to a platter. Drizzle with some of the tomato oil and sprinkle with flaky sea salt. Serve the beef warm or at room temperature with the pickled green tomatoes.