Preheat the air fryer: Set your air fryer to 390°F (200°C).
Lightly spray the basket to prevent sticking.
Toss the sweet potatoes: In a bowl, combine cubed sweet potatoes with 1 tablespoon oil and 1/2 teaspoon of the salt. Toss until coated.
Air fry until caramelized: Arrange the sweet potatoes in a single layer. Cook for 14–18 minutes, shaking halfway, until edges are browned and centers are tender.
Thicker cubes may need a few extra minutes.
Sauté the aromatics: While the potatoes cook, heat a medium pot over medium heat with a splash of oil. Add onion and the remaining 1/2 teaspoon salt. Cook 3–4 minutes until translucent.
Stir in garlic and ginger; cook 30–60 seconds until fragrant.
Bloom the curry paste: Add 2 tablespoons red curry paste to the pot and stir for 1 minute. This step intensifies the flavor. If you like more heat, add the third tablespoon now or later to taste.
Add liquids: Pour in the coconut milk and broth, stirring to combine.
Bring to a gentle simmer.
Combine with sweet potatoes: When the sweet potatoes are done, add them to the pot. Simmer 5–7 minutes to let flavors mingle.
Blend until smooth: Use an immersion blender to puree in the pot until silky. If using a countertop blender, work in batches and vent the lid slightly to release steam.
Blend to your preferred texture—ultra-smooth or a little rustic.
Adjust and brighten: Stir in lime juice. Taste and adjust salt. If it needs rounding out, add the sugar or maple syrup.
If you want more heat, stir in a bit more curry paste or a pinch of red pepper flakes.
Serve and garnish: Ladle into bowls and top with cilantro, green onions, and crushed peanuts or toasted coconut. Serve with lime wedges.