Cut vegetables to similar sizes for even cooking. Soak cashews at least 4 hours for a silky cream. Use an immersion blender for one-pot ease, or transfer to a blender in batches. Taste and add lemon at the end to brighten the soup. Cool the soup to room temperature before storing. Keep in an airtight container in the fridge for up to 4 days. Reheat gently on the stove and add a splash of water or broth if it feels too thick.