Roasted beef tenderloin, served cold, is a perfect make-ahead dish for a picnic.
Prepare the beef: Preheat the oven to 500°. In a large glass baking dish, combine the soy sauce, maple syrup, shallots and curry powder. Add the beef and rub the soy mixture all over.
In an ovenproof skillet, heat the vegetable oil until almost smoking. Season the beef with salt, add to the skillet and cook over moderately high heat until browned, about 15 minutes. Transfer the skillet to the oven and roast the meat for about 20 minutes, or until it reaches 125° on an instant-read thermometer for medium rare. Transfer the roasts to a cutting board and let stand until cooled.
Prepare the vegetables: In a pot of boiling salted water, cook the sugar snaps for 1 minute. Using a slotted spoon, transfer them to a colander set under cold running water; drain, pat dry and transfer to a large bowl. Repeat with the lima beans, cooking them until just tender, about 4 minutes; add them to the peas.
In a small skillet, toast the curry powder over low heat, stirring, for 2 minutes; transfer to a plate. Add the mustard seeds to the skillet and cook for 2 minutes; transfer to another plate.
In a bowl, combine the curry powder, oil, vinegar, garlic, lemon zest and salt.
Cut each roast into 1/4-inch-thick slices. Add the radishes, cucumbers, chives, mustard seeds and 1/2 cup of the curry vinaigrette to the sugar snaps and lima beans and toss. Serve the beef with the vegetables and pass the remaining vinaigrette separately.
Make Ahead: The roasted beef and the cooked peas and beans can be refrigerated separately overnight.