Curried Potato and Spinach Soup with Onion Salsa and Minted Yogurt

For mustard-onion salsa:

Combine first 5 ingredients in heavy medium saucepan. Cook over medium-high heat until onions begin to soften, stirring frequently, about 4 minutes. Reduce heat to low, cover, and cook until onions are very soft, stirring occasionally, about 40 minutes. Add lemon juice and lemon peel; cook uncovered until most liquid is evaporated, stirring often, about 10 minutes. Season with salt and pepper. Can be made 1 day ahead. Cover and chill. Rewarm before serving.

For curry oil:

Cook oil and curry powder in heavy small skillet over medium-high heat until curry powder darkens slightly, about 1 minute. Transfer to small pitcher. Can be made 1 day ahead. Cover and chill. Let stand at room temperature 1 hour before serving.

For minted yogurt:

Mix yogurt, green onions, and chopped mint in medium bowl. Cover and chill. Can be made 6 hours ahead. Keep chilled.

For soup:

Heat oil in heavy large pot over high heat. Add next 5 ingredients. Cook until onion and cauliflower begin to brown, stirring often, about 5 minutes. Add potatoes; stir 2 minutes. Add turmeric and stir 1 minute. Add broth and bay leaves. Bring to boil, reduce heat to medium, and simmer until vegetables are tender, about 10 minutes. Add spinach and stir until wilted, about 1 minute. Add tofu; heat until warmed through, about 1 minute. Season with salt and pepper. Discard bay leaves.

Divide soup among 6 bowls; sprinkle with chopped parsley. Serve salsa, curry oil, and minted yogurt alongside.

Nigella seeds are pungent and peppery, from a flowering plant of the same name. Also called kalonji or black onion seeds. Available at indianfoodsco.com.