1. Heat the olive oil in a medium saucepan and add the onion. Sauté until softened, about 5 minutes. Add the garlic, tomatoes, smoked paprika, sugar, chili powder, hot sauce, and lemon juice and bring to the boil, stirring. Reduce the heat and simmer for 10 minutes. Using an immersion or standard blender, puree until smooth. Season with salt and set aside or refrigerate for up to 24 hours.
2. Preheat the oven to 400°F. Place the potatoes and oil in an ovenproof skillet or baking pan and toss to combine. Roast for 45 to 50 minutes, or until the potatoes are crispy and golden brown.
3. Tip the baked potatoes into a serving dish and spoon the sauce over the top. Stir to combine. Sprinkle with the parsley and serve with a bowl of mayonnaise for dipping.