How to Make It
Combine 3 cups water, onion wedges, garlic, bay leaf, and 1/2 teaspoon salt in a medium saucepan over high; bring to a boil. Add lima beans, and return to a boil. Reduce heat to low, and simmer until beans are tender, 15 to 20 minutes. Drain; discard bay leaf. Spread bean mixture in a single layer on a baking sheet, and refrigerate until cold, about 30 minutes.
Combine basil, oil, vinegar, lemon juice, honey, pepper, and remaining 1/2 teaspoon salt in a blender; process until smooth, about 1 minute, scraping down sides of blender as needed.
Combine lima bean mixture, corn, tomatoes, and lentils in a large bowl; gently toss to combine. Divide lettuce among 4 plates; top evenly with bean mixture. Drizzle with basil vinaigrette; garnish with thin slices of red onion.