Some people love salads for the flavor or the health benefits. We agree on both counts, and there's an extra element to love about this salad in particular: the crunch. There's lettuce, of course, but also toasted walnuts and the crowning achievement of satisfying chomps, “everything bagel” croutons that you make yourself. We contrast the crunch with a little Fuji apple and onion, both made soft and delicious on the grill.
Cut baguette into 1" cubes. Halve apple, core, and cut into ¼" slices. Peel onion and slice into ¼" rounds. Halve grape tomatoes. Coarsely chop capers. Combine 2 Tbsp. olive oil, Champagne vinegar, honey, and a pinch of salt in a medium mixing bowl. Set aside to let flavors marry.
Toast the Walnuts
Place walnuts on prepared baking sheet. Spread into a single layer and toast until lightly browned, 5-7 minutes. Remove walnuts to a plate and reserve baking sheet with foil.
Make the Croutons
Add baguette cubes, 1 Tbsp. olive oil, and seasoning to reserved baking sheet. Toss to coat evenly, and spread into a single layer. Bake until golden brown, 7-9 minutes. While croutons bake, preheat a grill or grill pan over medium heat and lightly coat with cooking spray.
Grill Apples and Onions
Add apple slices to hot grill or grill pan cut side down and cook undisturbed until lightly charred, 3-5 minutes per side. Transfer apples to bowl with vinaigrette. Toss onions with 1 tsp. olive oil in a small mixing bowl. Place onions on grill and cook undisturbed until lightly charred and tender, 4-6 minutes per side. While onions cook, make salad.
Make the Salad
Add grilled onions, arugula, grape tomatoes, and capers to bowl with vinaigrette and apples. Toss to combine. Season to taste with salt and pepper.
Plate the Dish
Serve salad on a plate. Top with croutons and walnuts.