How to Make It
Squeeze the lemon half into a bowl of cold water and add the lemon half to the water. Working with 1 baby artichoke at a time, cut off the top one-third of the leaves and trim the stem to 1/2 inch. Pull off the tough outer leaves until you reach the tender yellow ones. Quarter the artichoke lengthwise and drop the quarters into the lemon water.
In a large skillet, heat 3 tablespoons of the olive oil until shimmering. Add the sunchokes, season with salt and pepper and cook over moderately high heat, stirring frequently, until tender and browned, about 12 minutes. Add 1/2 cup of the stock and cook, scraping up any browned bits from the bottom of the skillet, until the stock is reduced to a syrupy glaze, about 2 minutes. Season with salt and pepper and transfer the sunchokes to a plate.
Drain the baby artichokes and pat them dry. Wipe out the skillet; add 3 tablespoons of the olive oil and heat until shimmering. Add the baby artichokes and cook over moderate heat, turning occasionally, until crisp-tender and browned, about 5 minutes. Add the garlic and thyme sprig and cook until fragrant, about 30 seconds. Add the remaining 1/2 cup of stock and the 1 tablespoon of lemon juice and simmer until the artichokes are tender and glazed, about 5 minutes. Stir in the sunchokes and the spinach and cook over high heat just until the spinach wilts, about 1 minute. Discard the thyme sprig. Keep warm.
Light a grill or preheat a grill pan. Rub the salmon fillets with the remaining 1 tablespoon of olive oil and season with salt and pepper. Grill the salmon over a medium-hot fire until golden and cooked through, 2 minutes per side. Spoon the vegetables onto plates and top with the salmon. Drizzle the salad with the Warm Fennel Vinaigrette and serve.