Peel and cube two medium sweet potatoes into 1-inch pieces. Rinse 1¼ cups red lentils under cold water until clear, then set both aside.

Scatter chopped onion, minced garlic, and grated ginger in the slow cooker. Nestle sweet potatoes and rinsed lentils on top, then evenly dust with spices and salt.

Pour in 2 cups vegetable broth, a 14-oz can diced tomatoes, and 1 can coconut milk. Stir gently to combine all ingredients.

Cover and cook on low for 6–8 hours or high for 3–4 hours until lentils are creamy and sweet potatoes are tender.

Serve piping hot, garnished with fresh cilantro and a squeeze of lemon if desired.