Slow Cooker Bolognese - National Onion Association

Ingredients

• 1 tablespoon unsalted butter
• 1 large white onion, chopped
• 1 cup carrots, diced
• ½ cup diced celery
• 3 garlic cloves, minced
• 1 tablespoon chopped fresh parsley
• 1 pound lean ground beef
• 2 (6-ounce) cans tomato paste
• 1 (28-ounce) can crushed tomatoes
• 1 teaspoon fine sea salt
• ¼ teaspoon ground black pepper