Preheat oven to 400 degrees.
Put five tablespoons of olive oil, the fresh lemon juice and minced garlic in a large plastic bag. Add four boneless, skinless chicken breasts and coat them with the olive oil mixture.
Remove the chicken from the bag, reserving the olive oil mixture, and place it in a 12 inch cast iron skillet (can also use a casserole dish or 9 x 13" pan) greased with one tablespoon of olive oil.
Put the cubed potatoes, halved grape tomatoes in the bag and coat them with the olive oil mixture.
Surround the chicken with the potatoes and tomatoes.
Sprinkle everything with kosher salt, freshly ground black pepper and rosemary.
Top each piece of chicken with two lemon slices.
Bake at 400 degrees for 40-50 minutes, until the chicken is fully cooked (internal temperature of 165 degrees) and the potatoes are tender. Brown under the broiler for two minutes, if desired.