Cook the sweet potato: Heat a little olive oil (or a splash of water if oil-free) in a large skillet over medium heat. Add the sweet potato and onion with a pinch of salt. Cook for 5–7 minutes, stirring occasionally, until the onion softens and the sweet potato starts to brown.
Add the garlic, tomato paste, oregano, smoked paprika and red pepper flakes. Cook for about 1 minute, stirring constantly. Letting the tomato paste fry for a minute makes it dramatically more delicious.
Stir in the diced Roma tomato, beans and vegetable broth. Cover and simmer for about 8–10 minutes, stirring occasionally, until the sweet potato is fork-tender and the liquid has reduced.
Make it creamy: Blend the soaked cashews, water and salt until completely smooth and creamy. You want it fairly pourable—more like heavy cream than cashew cheese. Stir in the cashew cream and Kalamata olives. Simmer uncovered for another 2–3 minutes. The sauce should be thick, creamy and cling lovingly to the beans and sweet potatoes.
Remove from the heat and stir in the lemon zest, lemon juice and parsley. Taste and adjust the salt, pepper and lemon. If the tomatoes are particularly acidic, a tiny drizzle of maple syrup or agave can round everything out.
