Slow Cooker Tuscan Bean Soup

Slow Cooker Tuscan Bean Soup Ingredients: - 2 cans (15 oz each) cannellini beans, drained and rinsed - 1 can (14.5 oz) diced tomatoes - 4 cups vegetable or chicken broth - 1 small onion, diced - 2 carrots, peeled and sliced - 2 celery stalks, sliced - 3 cloves garlic, minced - 1 teaspoon dried oregano - 1 teaspoon dried thyme - ½ teaspoon salt (adjust to taste) - ½ teaspoon black pepper - ½ teaspoon red pepper flakes (optional) - 1 Parmesan rind (optional, for extra flavor) - 3 cups chopped kale or spinach - 1 tablespoon olive oil - Juice of ½ lemon