Melt the coconut oil in a large pan over medium heat. Add the onion and cook for 5-6 minutes, stirring occasionally. Add the bell pepper, garlic, ginger, and salt and stir to combine. Cook for an additional minute.
Add the curry paste to the pan and cook for about a minute, stirring to coat the other ingredients. Add in the coconut milk and bring to a simmer. Stir in the vegetables. Simmer, stirring occasionally, for 15-20 minutes until the squash is fork-tender. Add the kelp, remove the pan from the heat and stir in lime juice. Taste and adjust salt and lime juice as necessary. Sprinkle with cilantro and cashews to serve.