Roasted Tomato and Lentil Soup with Grilled Sourdough Croutons

# Roasted Tomato and Lentil Soup with Grilled Sourdough Croutons

There's a reason tomato soup has never gone out of fashion. It's warming, deeply savoury, and hits something fundamental — the kind of food that feels like a reset button on a grey afternoon.

This version takes the classic up a notch by roasting the tomatoes first and adding red lentils for body, protein, and a creaminess that needs no cream at all. Grilled sourdough croutons finish it off with crunch and character.

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Why roasting the tomatoes makes all the difference

Tinned tomatoes are brilliant — genuinely useful and perfectly fine in most recipes. But when tomatoes are roasted, something different happens.

The heat concentrates the natural sugars, drives off excess water, and produces a deeper, more complex flavour through a process called the Maillard reaction. What you get is a soup base that tastes like it's been simmering all day, even when it hasn't.

Fresh or tinned? Either works here. Fresh tomatoes — particularly vine or plum — benefit most from roasting. If you're using tinned, drain a little of the liquid and roast the pulp on a lined tray. It sounds fussy but takes about 30 seconds of effort and genuinely transforms the result.

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What makes this work nutritionally

This isn't just a nice soup — it's a genuinely well-balanced meal, particularly if you're tracking macros or trying to get more protein and fibre into your day without thinking too hard about it.

Red lentils are the quiet hero here. A 100g dry portion delivers around 25g of protein and 11g of fibre. They also provide iron, folate, and slow-digesting carbohydrates that help keep energy levels steady. Crucially, they dissolve when cooked, meaning they blend seamlessly into the soup without any lentil-specific texture that some people find off-putting.

Tomatoes contribute vitamin C, potassium, and lycopene — an antioxidant that, interestingly, becomes more bioavailable when tomatoes are cooked or processed rather than eaten raw. Roasting amplifies this further.

Sourdough croutons add satisfying crunch alongside some carbohydrate for energy. Sourdough's long fermentation process partially breaks down phytic acid, which can improve mineral absorption compared to standard bread — a modest but real nutritional advantage.

The overall macros per serving sit at roughly 350–400 kcal, with around 18–22g of protein, 8–10g of fibre, and a modest fat content depending on how generously you use the olive oil.

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Ingredients

Serves 4

For the soup: - 800g vine or plum tomatoes (or 2 x 400g tins of plum tomatoes, drained slightly) - 1 large white onion, roughly chopped - 4 garlic cloves, unpeeled - 150g red split lentils, rinsed - 700ml vegetable stock - 2 tbsp olive oil - 1 tsp smoked paprika - ½ tsp ground cumin - Salt and black pepper - A small handful of fresh basil (optional, stirred in at the end)

For the grilled sourdough croutons: - 2 thick slices of sourdough bread, torn into rough chunks - 1 tbsp olive oil - ½ tsp garlic granules - A pinch of sea salt

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Method

Step 1 — Roast the tomatoes and garlic

Preheat your oven to 200°C (fan 180°C / gas 6). Halve the fresh tomatoes and place them cut-side up on a large baking tray with the unpeeled garlic cloves. Drizzle with one tablespoon of olive oil, season well, and roast for 35–40 minutes until the tomatoes are collapsed and slightly caramelised at the edges. If using tinned, spread the drained pulp across the tray and roast for 20–25 minutes.

Step 2 — Cook the base

While the tomatoes roast, warm the remaining tablespoon of olive oil in a large saucepan over a medium heat. Add the onion with a pinch of salt and cook for 8–10 minutes until softened and translucent. Add the smoked paprika and cumin, stir for 60 seconds to bloom the spices, then add the rinsed lentils and vegetable stock. Bring to a simmer.

Step 3 — Bring it together

Once the tomatoes are done, squeeze the roasted garlic out of its skins and add it to the pan along with all the tomatoes and any roasting juices — this liquid is packed with flavour, so don't leave it behind. Simmer everything together for 15–20 minutes until the lentils are completely soft and beginning to break down.

Step 4 — Blend

Use a stick blender to blitz the soup until smooth. If you prefer a slightly more textured result, blend three-quarters and leave the rest as is. Taste, adjust seasoning, and stir through a handful of torn basil if you're using it.

Step 5 — Make the croutons

Tear the sourdough into rough bite-sized chunks. Toss with olive oil, garlic granules, and a pinch of sea salt. Heat a griddle pan or dry frying pan over a high heat and cook the croutons for 2–3 minutes, turning occasionally, until golden and crisp on the outside with a little chew remaining in the centre.

Serve the soup in deep bowls with the croutons piled on top. A drizzle of good olive oil and a crack of black pepper are optional but worth it.

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Common swaps and variations

No sourdough? Any sturdy bread works — a seeded loaf or rye bread holds up well in the oven or pan. Avoid very soft white bread, which tends to go powdery rather than crisp.

Want more heat? Add a pinch of dried chilli flakes when you bloom the spices. A small fresh chilli roasted alongside the tomatoes also works beautifully.

Adding extra protein? A tin of white beans blended in with the lentils pushes the protein content higher without changing the flavour profile much. Greek yoghurt stirred in at serving is another option if you're not keeping it vegan.

Making it ahead? This soup keeps well in the fridge for up to four days and freezes brilliantly for up to three months. Make the croutons fresh — they don't survive storage well.

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A note on batch cooking this

Soups like this are genuinely one of the most efficient things you can make in a batch cooking session. The effort involved in making four servings versus one is negligible, and having a portion in the fridge at the start of a busy week removes a lot of lunchtime friction.

The lentils also thicken the soup as it sits, so when reheating, add a splash of water or stock and stir well before serving. It won't affect the flavour — if anything, the taste deepens after a day in the fridge.

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Practical takeaways

• Roast your tomatoes — even tinned ones. Twenty-five minutes in the oven transforms the depth of flavour.
• Don't skip the roasting juices — they carry concentrated flavour and should go straight into the pot.
• Bloom your spices — cooking the paprika and cumin briefly in the oil before adding liquid makes a noticeable difference to the overall flavour.
• Tear, don't cut, the croutons — rough edges catch the heat and crisp up better than neat cubes.
• Batch cook it — this scales up easily to 8 portions and freezes well.

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