How to Make It
In a small skillet, toast the mustard seeds over moderately high heat until they pop, about 1 minute. Transfer to a small plate. Add 1 tablespoon of the oil to the skillet and when it is hot, add the curry powder. Cook over moderate heat until fragrant, about 1 minute. Scrape the curry oil into a medium bowl and let cool.
In a small saucepan of boiling salted water, cook the snow peas until bright green, about 1 minute. Drain and cool under cold water; pat dry with paper towels. Cut the snow peas lengthwise into thin strips.
In a medium bowl, gently toss the avocado with the lemon juice. Whisk the vinegar, dill, sugar and remaining 3 tablespoons of vegetable oil into the curry oil and season with salt. Add the snow peas, red pepper, onion and tuna to the dressing and toss. Gently fold in the avocado and serve.