Slow-Cooker Sweet Potato and Lentil Soup

INGREDIENTS

• 1/2 cup chopped fresh cilantro
• Kosher salt
• 2 leeks, halved lengthwise and cut into 1/2-inch pieces (white and light green parts only)
• 3 medium carrots, cut into 1/2-inch pieces
• 1 teaspoon curry powder
• 1 large sweet potato, peeled and diced
• 1 4-inch piece ginger, peeled and finely grated
• 3 stalks celery, cut into 1/2-inch pieces
• 1 tablespoon unsalted butter
• Juice of 1/2 lemon, plus lemon wedges for serving (optional)
• 2 cloves garlic, thinly sliced
• 3/4 cup dried yellow or red lentils