Step 1: Prepare the chicken. Pat chicken breasts dry. Rub with 1 tbsp olive oil, season generously with salt, pepper, and garlic powder. Heat a grill or grill pan over medium-high heat. Grill chicken for 5-7 minutes per side, or until internal temperature reaches 165°F (74°C) and it has nice grill marks. Remove from heat and let rest for 5 minutes before slicing into bite-sized pieces.
Step 2: Dice the watermelon and slice the red onion. While the chicken rests, dice the watermelon into approximately 1-inch cubes. Using a sharp knife or mandoline, very thinly slice the red onion. If the onion is too pungent for your taste, soak the slices in ice water for 10-15 minutes, then drain and pat dry.
Step 3: Prepare the mint-lime vinaigrette. In a small bowl, whisk together the fresh lime juice, 1/4 cup extra virgin olive oil, honey (if using), finely minced mint, salt, and pepper until well combined.
Step 4: Assemble the salad. In a large serving bowl, gently combine the diced watermelon, sliced grilled chicken, thinly sliced red onion, and crumbled feta cheese. Add the roughly chopped mint leaves.
Step 5: Dress and serve. Pour the prepared mint-lime vinaigrette over the salad ingredients. Gently toss to ensure all components are lightly coated. Serve immediately to enjoy the salad at its freshest.