Why roasting transforms a salsa

A raw pepper salsa is bright and crunchy, but thin and watery when it meets a hot dog bun. Roasting changes everything. The flesh softens, the water cooks off, and the sugars concentrate until the whole thing turns almost jammy. Blistered skin adds a gentle bitterness that keeps the sweetness in check, and the finished salsa is silky enough to cling to a sausage rather than sliding off onto the plate.

This one is built around roasted red peppers and roasted garlic, with smoked paprika and cumin pushing things in a warm, smoky direction. It takes about an hour, most of it hands-off, and a batch keeps for the best part of a week.

Choosing your peppers, chillies and garlic

Pointed romano peppers are ideal: thinner-fleshed than bells, so they roast quickly and taste sweeter. Standard red bells work well too, but hold more water, so drain them properly later. Avoid green peppers — they're grassy and bitter, and the salsa will taste underripe.

A few other things earn their place in the tin:

• One or two red chillies, halved and deseeded, for background heat — or leave them out and lean on the paprika.
• A whole head of garlic, cloves separated but unpeeled, which roast to something soft, sweet and nutty.
• Half an onion in thick wedges, for depth. It goes jammy at the edges.
• A teaspoon of cumin seeds and a couple of sprigs of thyme, added for the last ten minutes.

Short on time? A jar of good roasted peppers will do. Drain and pat them dry, then add an extra pinch of smoked paprika to make up for the missing char.

Roasting the peppers properly

Heat the oven to 200°C fan (220°C conventional, gas mark 7). Halve the peppers, scoop out the seeds and white pith, and flatten them with the palm of your hand. Lay them skin-side up in a roasting tin in a single layer — crowded peppers steam rather than roast. Tuck the garlic cloves and onion wedges into the gaps.

Give them 25 to 35 minutes, until the skins are blackened in patches and the flesh has slumped. The garlic will be ready sooner; check at 15 to 20 minutes and pull it out once the cloves feel soft when squeezed.

Then the important bit: tip the peppers into a bowl, cover tightly with a plate, and leave for 10 minutes. The steam loosens the skins and they'll slip off with your fingers. Don't rinse them. Every scrap of blackened skin you leave behind is flavour, so scrape off only the loosest bits.

You can also hold the peppers over a gas flame with tongs until charred all over, then steam and peel as above — a good option if you're cooking outdoors anyway.

Building the salsa

Once the peppers are peeled and cooled, you're five minutes from a finished salsa. This makes enough for six to eight hot dogs.

• 500g roasted pepper flesh, roughly chopped
• 6 to 8 roasted garlic cloves, squeezed from their skins
• 1 tbsp sherry vinegar, or red wine vinegar
• 1 tsp smoked paprika
• ½ tsp ground cumin
• 3 tbsp extra virgin olive oil
• ½ tsp fine sea salt, plus more to taste
• A pinch of caster sugar, only if needed
• A handful of chopped coriander or flat-leaf parsley

Chop the peppers by hand rather than blitzing everything — you want texture, not purée. Mash the garlic to a paste with the salt, then stir everything together. For a looser, silkier result, pulse a third of the mixture in a small blender and stir it back in. Leave to sit for at least 30 minutes before serving; it's better still the next day.

Balancing the heat, sweetness and smoke

Taste before serving and adjust. Salsas are forgiving, but a few problems come up often:

• Too watery: tip it into a sieve for 20 minutes, or stir in a spoonful of tomato purée.
• Too sharp: a pinch of sugar, or another drizzle of oil.
• Too sweet: a squeeze of lime or a splash more vinegar.
• Too hot: more pepper flesh, or a spoonful of mayonnaise if you don't mind it going creamy.
• Too acrid: you've kept too much heavily blackened skin. Fish out the darkest pieces and add a little more oil.

You want smoke sitting in the background, warm and rounded, rather than shouting over everything else.

Serving it with hot dogs and sausages

This salsa is at its best with sausages that have some richness and smoke of their own — a good Cumberland, a smoked pork frankfurter, something chorizo-style, or a well-charred chicken or veggie banger. Serve it at room temperature or gently warmed; fridge-cold kills the aroma.

A few things that work alongside it:

• Crispy fried shallots, scattered at the last moment for crunch.
• Quick-pickled red onion, to cut through the richness.
• Crumbled feta or coarsely grated mature cheddar.
• A squeeze of lime and a few coriander leaves just before serving.

Toast the buns cut-side down in the pan you cooked the sausages in — thirty seconds is plenty — then spoon the salsa along the base before the sausage goes in, so it soaks into the bread instead of landing on your shirt.

It keeps in the fridge for five days, covered with a thin layer of oil, and freezes for up to three months. It's also very good on burgers, folded through roast potatoes, or spooned over fried eggs the morning after.