1. Preheat your grill to medium-high heat.
2. In a bowl, combine olive oil, lemon zest, lemon juice, minced garlic, salt, and pepper.
3. Toss the chicken tenderloin in half of the lemon-garlic mixture and let it marinate for at least 20 minutes.
4. Meanwhile, preheat your oven to 400°F (200°C).
5. Arrange asparagus on a baking sheet and drizzle with the remaining lemon-garlic mixture. Toss to coat evenly.
6. Roast asparagus in the oven for 10-15 minutes, or until tender and slightly crispy.
7. Place the marinated chicken tenderloin on the preheated grill and cook for 6-8 minutes on each side, or until fully cooked and golden brown.
8. Serve the grilled chicken tenderloin with roasted asparagus on the side.

Enjoy your delicious and nutritious meal!