Add the olive oil to a large nonstick skillet set over medium heat. When hot, add in the onion, pepper, sweet potato and salt. Cook for about 5 minutes, until the veggies start to soften. Stir in the curry paste until combined. Add in the coconut milk, broth, soy sauce, sugar, garlic and ginger, and mix to combine.
Increase the heat and bring the mixture just to a boil. Reduce the heat and simmer for about 12 to 15 minutes, stirring occasionally, until the sweet potato is tender. Turn the heat down to low and add in the pineapple and spinach. Cook for about 1 to 2 minutes, stirring frequently, until the spinach is wilted. Remove from the heat and stir in the cashews and lime juice.
Serve the curry over rice, with fresh basil for garnish.