Char red bell peppers over a flame or under the broiler until fully blackened. Steam in a sealed bag 5–10 minutes, then peel, seed, and chop.
Blend roasted peppers with hazelnuts, tomatoes, garlic powder, paprika, olive oil, lemon juice, and salt until smooth. Loosen with tomato juice if needed and adjust seasoning.
Break cooked baby potatoes into chunks and sauté in hot oil until deeply golden and crispy. Toss with black sesame paste and salt while hot.
Arrange smelt on a parchment-lined tray, drizzle with olive oil, and season with salt. Roast at 420°F until browned and lightly charred. Finish with togarashi or chili flakes.
Tear frisée and toss generously with lemon juice and salt.
Swipe romesco onto plates, add potatoes and frisée, then top with smelt. Finish with extra lemon juice and olive oil if desired.