This is everything you want in an entree salad—big, beautiful and colorful, hearty enough to satisfy and easy to put together. Zesty, peppery greens like watercress, endive and arugula add dimension while peaches and tomatoes contribute sweetness and tang. Make the creamy lemon-herb dressing and prep the veggies ahead of time and you'll only need to spend a few minutes at the grill before dinner.
For the dressing: whisk together the buttermilk, mayonnaise, sour cream, olive oil and lemon juice in a medium bowl. Add the lemon zest, 1/2 teaspoon salt, 1 1/2 teaspoons pepper, parsley, chives, dill and garlic and whisk until smooth. Refrigerate while you make the salad.
For the salad: sprinkle the steak all over with the coriander and paprika. Season with salt and pepper and brush with olive oil. Grill the steak until well charred, flipping once, about 4 minutes per side for medium rare, depending on the thickness of the steak. Let rest on a cutting board while you assemble the salad.
Scatter the arugula, watercress and red endive on a large serving platter. Arrange the tomatoes, peaches and radishes over the greens. Sprinkle with herbs, feta and sunflower seeds.
Thinly slice the skirt steak across the grain and arrange on a platter over a swipe of lemon-herb dressing. Top with flaky sea salt and more herbs. Serve the steak and remaining dressing alongside the salad.