Place a slow cooker liner in the bowl of your slow cooker or spray with nonstick cooking spray.
Add sliced onions and garlic to the bowl and then cover with chicken breasts.
Add chopped tomatoes, balsamic vinegar, olive oil, crushed red pepper (if using), salt and pepper.
Cover and cook on low for 7-8 hours or high for 3-4 hours.
Shred chicken (it should literally fall apart), add basil and top with grated mozzarella cheese. Turn slow cooker on high and cover until the cheese has melted.
Serve with brown rice, quinoa or whole grain pasta. Or for a lower carb meal, serve alone.
Notes
Nutritional information is for the chicken only.
Recipe by Becky's Best Bites at https://beckysbestbites.com/slow-cooker-chicken-caprese/