Lemony Chicken Breasts with Rice

4 Tbsp. unsalted butter
1 onion, finely chopped
2 garlic cloves, finely chopped
4 boneless chicken breast halves
Salt and Pepper
4 Cups canned low-sodium chicken broth
1/4 cup lemon juice
2 Cups long-grain rice
1/4 cup finely chopped fresh parsley

Melt 2 tbsp butter in a large skillet over medium high heat. Add onion and cook until softened, stirring occasionally, 4 to 5 minutes. Add garlic and cook 1 minute longer. Scrape into slow cooker. Sprinkle chicken with salt. Melt remaining 2 tbsp butter in skillet over medium high heat until foaming. Add chicken breast halves and cook until browned, about 2 minutes per side. Transfer to slow cooker. Add 1 cup broth and lemon juice to skillet and bring to a boil, scraping browned bits from bottom of pan. Add to the slow cooker, along with remaining broth, rice and 1 tsp salt. Stir, cover and cook on low until chicken is cooked through and rice is tender, 2 to 3 hrs. Remove chicken, stir parsley into rice and season with salt and pepper.