Heat the olive oil in a large skillet over medium heat. Add the carrots, onion and a pinch of salt and cook, stirring, until soft and translucent, 10 to 12 minutes. Add the garlic, cumin, harissa, paprika, pepper flakes, a good pinch of salt and a few turns of black pepper and cook until it's all dreamy and smelly, about 2 minutes. Stir in the tomato paste, then the chopped tomatoes and sugar. Reduce the heat to low, then stir in the pasta and stock. Cover and simmer, stirring occasionally, about 15 minutes.
Sprinkle bowls of soup with black pepper, drizzle with olive oil and top with the feta and herbs.