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Slow-Roasted Tomato Soup That Earns Its Time

📅 March 10, 2025 🍵 Soups 🌱 Vegan ⏱ 2 hours 20 minutes

Most tomato soups taste like tinned tomatoes that have been warmed up. This one does not. Two hours at a low oven temperature concentrates the tomatoes' natural sugars, evaporates their excess water, and produces a flavour that is intense, sweet-acid, and genuinely complex — more like a sauce than a broth, more like summer than anything you'd pour from a carton.

The technique is called slow roasting, and it's less a recipe than a principle: apply low, even heat to a vegetable for long enough, and its character transforms. Tomatoes respond to this treatment better than almost anything else. What begins as a tray of supermarket rounds — watery, slightly acidic, smelling of greenhouse plastic — becomes something sticky, concentrated, and deeply savoury after two hours at 150°C.

On Using Supermarket Tomatoes

The most common objection to this soup is that it requires good tomatoes. It doesn't, and that's precisely the point. The slow-roasting technique is designed for ordinary tomatoes — the kind available year-round at any supermarket. Peak-season, vine-ripened tomatoes from a farmers' market will obviously produce a better result, but the transformation is equally dramatic with everyday tomatoes, and the improvement over the raw fruit is profound regardless of starting quality.

Use vine tomatoes if available, as the vines impart additional flavour during roasting. Roma (plum) tomatoes also work excellently due to their lower water content and meatier flesh.

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🍅 Slow-Roasted Tomato Soup
Prep
15 min
Roast
2 hrs
Total
2 hr 20 min
Serves
6
Diet
Vegan

Ingredients — Soup

  • 1.5kg vine or plum tomatoes, halved
  • 1 whole head of garlic, halved horizontally
  • 2 medium white onions, quartered
  • 4 tbsp extra virgin olive oil
  • 1 tsp caster sugar
  • 1 tsp flaky salt + more to taste
  • 1 litre vegetable stock
  • 1 tsp smoked paprika
  • Freshly cracked black pepper

Ingredients — Crispy Chickpeas

  • 1 × 400g tin chickpeas, drained and patted dry
  • 2 tbsp olive oil
  • ½ tsp smoked paprika
  • ¼ tsp cayenne (optional)
  • Salt to taste

Method

  1. 1
    Preheat your oven to 150°C / 300°F. Arrange the tomatoes cut-side up in a large roasting tray along with the onion quarters. Nestle the halved garlic head in the centre. Drizzle everything with the olive oil, sprinkle with sugar, salt, and a few cracks of black pepper.
  2. 2
    Roast for 1 hour 45 minutes to 2 hours. The tomatoes should have collapsed, darkened at the edges, and reduced significantly in size. The onions will be soft and slightly caramelised. Don't rush this — the time is the recipe.
  3. 3
    While the tomatoes roast, make the chickpeas. Increase oven to 200°C, toss the dried chickpeas with olive oil, paprika, cayenne, and salt on a baking tray, and roast for 25–30 minutes until golden and crisp. Set aside.
  4. 4
    Squeeze the roasted garlic cloves out of their skins into a large saucepan. Add all the roasted tomatoes and onions, including all the oil and juices from the tray. Add the stock and smoked paprika. Bring to a simmer.
  5. 5
    Use a stick blender to blitz the soup until very smooth. For an especially velvety result, pass it through a fine-mesh sieve. Taste and adjust seasoning — it will likely need more salt.
  6. 6
    Serve in warm bowls topped generously with crispy chickpeas and a drizzle of good olive oil. Add a swirl of oat cream or plant-based yoghurt if you like.
💡 Make ahead: The soup (without chickpeas) keeps refrigerated for up to 5 days and freezes beautifully. Make the chickpeas fresh when serving — they go soft if stored with the soup.

Why This Method Works

Low, slow heat allows moisture to evaporate gradually while the sugars in the tomato concentrate and begin to caramelise at their edges. High heat would achieve some of this but also risks charring the skin before the interior has had time to collapse and concentrate. The two-hour process is genuinely passive — you put the tray in, set a timer, and get on with other things.

Serving Ideas

The crispy chickpeas are not optional decoration — they provide textural contrast that makes the soup interesting rather than merely comforting. Other good toppings: toasted sourdough croutons, a spoonful of basil oil, or a few leaves of fresh thyme scattered over the surface just before serving. Grilled cheese on the side is never wrong.