Preheat your Traeger Grill or conventional grill to 500F.
Add the pecans to a dry, cold skillet and place over medium-low heat. Toast the pecans, stirring often, until warmed through and lightly golden. Transfer the pecans to a cutting board, let them cool and then roughly chop them with a knife. Transfer to a bowl and set aside until ready to use.
In a small bowl, combine the onion powder, garlic powder, smoked paprika, thyme, ½ teaspoon salt and ¼ teaspoon pepper. Place the salmon on a tray or board, drizzle with 2 tablespoons avocado oil and massage to coat. Evenly season both sides with the spice rub. Set aside.
Trim and discard the bottom tips of the kale stalks. Drizzle the leaves with 2 tablespoons avocado oil, season with ½ teaspoon salt and toss to coat.
Transfer the lemon halves, kale and fish to the grill, skin-side down first, and cook until grill marks form, 5 to 6 minutes. Using a fish spatula, carefully flip the fish and cook the flesh side until the thickest part of the fish is flakey and opaque, 5 to 6 more minutes. Grill the kale, flipping once or twice, until lightly charred, around 8 minutes total. Grill the lemon halves until the flesh is charred, around 10 minutes total. Transfer everything to a board or tray.
While still warm, roughly chop the kale and add it to a large salad bowl along with the hearts of palm, shallot, tomatoes, barberries, and chopped pecans. Drizzle with the Charred Lemon Vinaigrette (see below) and toss everything to coat. Transfer the salad onto individual serving plates, top with a filet of salmon and serve warm or at room temperature.