Directions

• Cook bacon in a skillet over medium, stirring occasionally, until just crispy, about 5 minutes. Transfer bacon to paper towels; reserve drippings in skillet.
• Preheat grill to medium-high (400°F to 450°F). Brush corn and onion evenly with 1 tablespoon oil; sprinkle evenly with 1/2 teaspoon salt and 1/4 teaspoon pepper. Arrange on oiled grates; grill, uncovered, flipping onion slices once and corn occasionally, until lightly charred, about 5 minutes per side for onion and 12 to 15 minutes total for corn. Transfer to a cutting board; let cool 5 minutes. Separate onion slices into rings. Cut corn kernels from cobs; discard cobs. Set onion rings and corn kernels aside until ready to use.
• Brush salmon on both sides with reserved bacon drippings; sprinkle with 1 teaspoon salt and 1/2 teaspoon pepper. Place salmon, skin side down, on oiled grill grates; grill until lightly charred, about 4 minutes. Flip salmon, and grill until char marks appear and salmon is cooked through, 3 to 4 minutes. Transfer to a plate; let stand until cool enough to handle, about 5 minutes. Remove and discard salmon skin, and break salmon into large chunks. Cover loosely with aluminum foil to keep warm; set aside.
• Whisk together vinegar, mustard, tarragon, honey, 1 tablespoon water, remaining 1/4 cup oil, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper in a bowl. Toss together lettuce, watercress, and 1/2 cup dressing on a large platter; season with additional salt and pepper to taste. Arrange bacon, onion, corn, salmon, eggs, avocado, and tomatoes on greens. Serve with remaining dressing.