Jen Grilled Chicken with Avocado Tzatziki

Jen Grilled Chicken with Avocado Tzatziki 6 boneless skinless chicken breasts2 lemons (juiced, divided)2 tablespoons olive oilsea salt and freshly ground black pepper (to taste)2 large avocados (peeled and chopped)2 cloves garlic (minced)1 serrano chili (seeded and...