Skirt Steak with Roasted Tomato Chimichurri and Potatoes

Preheat the oven to 400°. On a large rimmed baking sheet, toss the tomatoes with 1/4 cup of the olive oil and season with salt. Roast for about 20 minutes, until softened and browned in spots; let cool slightly. Transfer the tomatoes to a food processor. Add the parsley, vinegar, crushed pepper and the remaining 1/4 cup of oil. Pulse until almost smooth. Season with salt and transfer to a bowl.

In a saucepan, cover the potatoes with water and bring to a boil. Add a generous pinch of salt and simmer over moderate heat until tender, about 15 minutes. Drain the potatoes and let cool, then halve lengthwise.

In a large skillet, heat the olive oil until shimmering. Add the onion and cook over moderately high heat, stirring, until just softened, about 3 minutes. Add the potatoes cut side down and cook until browned on the bottom, about 5 minutes. Flip the potatoes and onion and cook, stirring, until well browned, about 4 minutes. Stir in the butter and parsley and season with salt. Transfer to a platter and keep warm.

Light a grill or preheat a grill pan. Season the steaks with salt and black pepper. Grill over high heat, turning once, until medium-rare, about 7 minutes total. Transfer to a carving board and let rest for 10 minutes. Thinly slice the steak across the grain and transfer to the platter with the potatoes. Serve with the tomato chimichurri.