Roast the potatoes: Preheat oven to 200 °C. Toss sweet potato cubes with olive oil, paprika, salt, and pepper. Spread out on a tray and roast 25–30 min until golden and crisp at the edges.
Make the bravas sauce: While roasting, heat olive oil in a small pan. Add onion and cook until soft. Stir in garlic, paprika, and chilli flakes; cook 30 sec. Add tomatoes and vinegar, simmer 10 min until thick. Season.
Blend or mash: Blend if you want a smooth sauce, or mash lightly for rustic texture.
Mix the aioli: Stir together mayo, smoked paprika, lemon, and salt.
Assemble: Pile sweet potatoes on a plate, spoon over bravas sauce, and drizzle aioli across the top.
Notes
Elevate it: Sprinkle chopped chives or crispy onions.
Prep ahead: Bravas sauce keeps 3 days chilled; reheat gently. Aioli can be made a day ahead.