Preheat the oven to 200°C (400°F).
Toss the cubed potatoes with olive oil, salt, and pepper. Spread them on a baking sheet and roast for 30-35 minutes until crispy and golden.
Meanwhile, prepare the bravas sauce. Heat olive oil in a pan over medium heat. Add onion and cook until soft, about 5 minutes.
Add garlic, smoked paprika, and hot paprika (if using). Cook for another minute until fragrant.
Stir in tomato paste, tomato sauce, red wine vinegar, salt, pepper, and sugar (if using). Simmer for 10 minutes, stirring occasionally, until the sauce thickens.
Once potatoes are done, transfer them to a serving dish. Pour the bravas sauce over the potatoes.
Serve hot as a delicious tapas dish or side.