Place marinade ingredients in a large jar and seal with a tight-fitting lid. Shake vigorously to combine and set aside.
Place chicken breast cubes in a large glass bowl and pour the marinade on top. Gently toss to combine, ensuring the chicken is evenly coated on all sides. Cover and place in the refrigerator for 30 minutes to one hour.
Remove chicken from the refrigerator 15 minutes before cooking. Drain and discard the marinade.
Thread a tomato onto a skewer, followed by two pieces of chicken. Then add another tomato, two more pieces of chicken, and a third tomato on the end. Repeat with the remaining chicken and tomatoes on the remaining skewers. If there are additional chunks of chicken leftover, place them on another skewer and cook with the rest.
Spray a large grill pan with non-stick cooking spray (or brush with a neutral oil with a high smoke point) and set over medium-high heat. Once hot, add the skewers to the grill pan and cook for 4-5minutes, or until they release easily from the surface. Flip each skewer and cook on the remaining side for another 4-5 minutes. Sear the remaining sides for 1 minute each.
Transfer the skewers to a platter and set them aside. Add the lemon halves to the hot grill pan and press down on each with a spatula. Heat until the exposed surface is warm and nicely browned, approximately 2 minutes. Remove from heat and squeeze the warm lemon halves over the chicken skewers right before serving. Enjoy!