Meanwhile, heat a dutch oven or heavy-bottomed pan over medium heat. Add 2 tsp. of coconut oil. Once melted, add half the yellow onion and the jalapeño and cook until fragrant and soft, 4 to 5 minutes. Stir in the garlic and ginger, cooking for another minute or so, then add the curry paste, lime juice, sugar, coconut milk and cilantro. Stir to combine, then bring to a simmer and cook for 5 minutes. Carefully pour into a blender (or use an immersion blender) and puree the sauce until smooth. Set the sauce aside and wipe out the pot.