Heat olive oil in a medium pot; add onion and garlic and sauté until soft, about 5 minutes. Stir in curry powder, ginger, and cumin and cook for 1 minute. Stir in lentils and broth; bring to a boil, reduce heat, and simmer, covered, for 10 minutes. Add sweet potatoes, cover, and cook for 10 minutes longer, until water is absorbed and sweet potatoes are just tender. Stir in baby spinach and cook for 1 minute longer, until spinach is just wilted. Add salt and adjust seasonings to taste.

Transfer to four serving bowls and top each with 1/4 cup yogurt and 2 tablespoons chopped almonds. Serve immediately.