Add thin chicken breasts to a plate and squeeze with a little lemon juice over them. Season lightly with salt, garlic powder, and pepper.
Coat a large nonstick pan with cooking spray. Add olive oil and heat over medium heat.
Add chicken breasts and cook them for approximately 3-4 minutes on each side until cooked through. Transfer the chicken to a clean serving plate.
Add ¼ cup wine or ¼ cup chicken broth and cook over medium heat until half the amount has evaporated, about 1½-2 minutes. Stir in ½ cup chicken broth and lemon juice. Return the chicken to pan and cook on each side for 1 minute. Remove chicken to serving plate. Leave the sauce in the pan.
To the pan of sauce, stir in tomatoes and scallions. Season with a little more salt, pepper, and garlic powder, if desired. Continue to cook for about 1-2 minutes, until thoroughly heated.
Pour tomatoes and sauce over chicken and serve.