Prepare the Quinoa:
1. In a medium saucepan, bring 2 cups of water or chicken broth to a boil.
2. Add the rinsed quinoa, reduce the heat to low, cover, and simmer for about 15 minutes, or until the quinoa is cooked and the liquid is absorbed.
3. Fluff the quinoa with a fork and set aside to cool.

Prepare the Chicken Tenderloin:
1. Preheat your grill or grill pan to medium-high heat.
2. In a small bowl, mix together the lemon juice, lemon zest, minced garlic, fresh dill or parsley, olive oil, salt, and pepper.
3. Brush the chicken tenderloin pieces with the lemon herb mixture.
4. Grill the chicken for about 5-6 minutes on each side, or until fully cooked and slightly charred. Remove from the grill and set aside.

Assemble the Quinoa Bowl:
1. In a large bowl, combine the cooked quinoa, diced cucumber, halved cherry tomatoes, shredded carrot, and baby spinach or mixed greens.
2. Slice the avocados and add them to the bowl.
3. Optional: Add thinly sliced red onion for extra flavor and texture.

Make the Dressing:
1. In a small bowl, whisk together the lemon juice, olive oil, honey or Dijon mustard if using, salt, and pepper until well combined.

Dress the Bowl:
1. Drizzle the dressing over the quinoa and vegetable mixture, and toss gently to combine.

Serve:
1. Divide the quinoa salad among individual serving bowls.
2. Top each bowl with a grilled chicken tenderloin piece.

Garnish:
1. Garnish with additional fresh herbs, lemon wedges, or a sprinkle of seeds or nuts for extra texture and flavor.

Serve:
1. Serve immediately and enjoy this vibrant and healthy Grilled Chicken Tenderloin and Avocado Quinoa Bowl!

Tips:
– For added variety, include other vegetables like roasted sweet potatoes or steamed broccoli.
– Add a pinch of red pepper flakes to the chicken marinade for a bit of heat.