Seared Flank Steak with Watercress Salad

From the garden

• 8 cups watercress, thick stems trimmed, washed and spun very dry · about 2 large bunches, 10 to 12 ounces
• 6 medium radishes, sliced paper-thin
• 2 medium shallots, sliced into thin rings
• ½ cup fresh mint, leaves torn
• ½ cup cilantro, leaves and tender stems, roughly chopped (optional)
• 2 cloves garlic, finely grated

From the pantry

• 1½ lb flank steak, patted dry
• 3 limes, juiced, about 6 tablespoons
• 3 tbsp fish sauce
• 1 tbsp sugar
• 2 tbsp vegetable oil
• ½ tsp red pepper flakes (optional)
• 1½ cups jasmine rice (optional) · cooked, for serving
• salt · to taste
• black pepper · coarsely ground, and plenty of it

1. Take the steak out of the fridge 20 minutes ahead. Season both sides hard with salt and coarse black pepper. Whisk the lime juice, fish sauce, sugar, garlic, and red pepper flakes in a small bowl until the sugar dissolves, then stir in the shallot rings and let them soften in the dressing while you cook.
2. Heat a heavy skillet (cast iron is ideal) over high heat until it just starts to smoke. Add the oil, lay in the steak, and leave it alone 4–5 minutes until a dark crust forms. Flip and cook 3–4 minutes more for medium-rare: 130–135°F in the thickest part. Flank goes tough past medium, so err on the early side.
3. Move the steak to a board and rest it a full 10 minutes. Do not skip this; the juices you save go into the salad.
4. While it rests, pile the watercress, radishes, and mint in a wide serving bowl or platter. It will look like too much cress. It is not.
5. Slice the steak thinly across the grain, holding the knife at a slight angle. Scatter the slices over the greens, pour any board juices into the dressing, then spoon the dressing with its shallots over everything. Toss lightly once at the table so the cress wilts only where it touches the warm meat.
6. Finish with cilantro and serve right away, with rice alongside if you want a heartier plate.