Halibut in Hazelnut Romesco with Potatoes

Preheat broiler. Place tomato on rimmed baking sheet and broil until skin is blistered and slipping off, turning once with tongs, about 3 minutes. When cool enough to handle, peel skin off tomato, then cut in half and squeeze out seeds.

Chop nuts in processor; add tomato, piquillo peppers, 2 tablespoons olive oil, garlic, paprika, vinegar, salt, and cayenne, then puree. Transfer romesco sauce to bowl. DO AHEAD: Can be made 1 day ahead. Cover and refrigerate.

Melt butter with remaining 2 tablespoons oil in heavy large skillet over medium-high heat. Add halibut and cook until golden brown, about 2 minutes per side (fish will not be cooked through). Transfer halibut to plate.

Add broth to same skillet and bring to boil; stir in romesco sauce. Add halibut; reduce heat to medium-low, cover, and simmer until halibut is opaque in center, about 2 minutes. Transfer halibut to plates. Place steamed potatoes alongside. Spoon romesco sauce over; sprinkle with parsley, if desired, and serve.

Sometimes labeled Pimentón Dulce or Pimentón de La Vera Dulce; available at some supermarkets, at specialty foods stores, and from tienda.com.