While your grill heats up, prepare all your ingredients for cooking. Slice the zucchini into 1/2-inch thick rounds and trim the woody ends off the asparagus. Pat the salmon fillets dry with paper towels—this helps them develop a better crust on the grill. Arrange the prepared vegetables and salmon on a large plate or cutting board, ready to go to the grill.

Heat your grill to medium-high heat (around 400°F). While it preheats, season the zucchini and asparagus with 1/4 teaspoon salt, 1/4 teaspoon black pepper, and 1/2 teaspoon garlic powder, then drizzle with 4 tablespoons of balsamic vinaigrette and toss to coat evenly. Season the salmon fillets with 1/4 teaspoon kosher salt, 1/4 teaspoon black pepper, and 2 teaspoons of balsamic vinaigrette, rubbing it gently onto the flesh side. Once the grill is hot, lightly oil the grates to prevent sticking.

Place the zucchini and asparagus directly on the grill grates and let them cook undisturbed for 3-4 minutes until they develop nice grill marks. Flip the vegetables and cook for another 3-4 minutes until they're tender with light char. While the vegetables are finishing, place the salmon fillets skin-side down on the grill. Let them cook for 8-10 minutes without moving them—this creates a crispy exterior while keeping the inside moist. I like to check if the salmon is done by gently pressing the thickest part; it should feel firm but still have a slight give.

Transfer the grilled salmon and vegetables to a serving platter or individual plates. Squeeze fresh lemon juice over the salmon and vegetables to brighten the flavors. Drizzle any remaining vinaigrette from the grill pan over the vegetables, or add extra balsamic vinaigrette if desired. Serve immediately while everything is still warm.