While not quite goats in trees, the caper plants that grow on the steep concrete embankments on either side of the Tiber river in Rome are quite remarkable. “How do they hold on?” asked my young son when we stopped to look at a great bushy cluster, before he was distracted by the apocalyptic pile of twisted yellow rental bikes that had clearly been hurled from the Roman pavement 10 metres above. The distraction of bike hooliganism meant I didn’t have to admit to having no idea how capers cling to sheer embankments, or that, until the age of 32, I thought capers were a variety of seaweed.

Capparis spinosa – Flinders rose, or the caper bush – is a rupicolous species, which means it can grow and thrive on rocks and crevices, withstand wind and the harshest environments. Capers grow in great tangles on sand dunes in Pakistan, the coastal deserts of Libya and Tunisia, on the volcanic soil of the Sicilian islands Pantelleria and Salina, they clamber the ramparts of medieval castles in Spain like free climbers ... and grow spontaneously on the Aurelian Walls in Rome. It was the trailing bunches clinging to a section of ancient city wall near my flat in Testaccio that taught me that the nubs of flavour on my pizza and the essential jolt of unabashed flavour in sauces, came from land, not sea.

A many-branched, shrubby plant with round, shiny leaves, the caper bush blooms from April to September, its buds opening to a showgirl flower with pink petals and long, violet-tipped stamens. It is the unopened bud, though, that is potentially edible. Bright green and ranging from the size of a peppercorn to a large pea, the buds need to be hand-picked, graded according to size – the smallest being the most desirable – then cured in brine before being preserved in either a fresh brine, wine vinegar or packed in coarse salt crystals. The mature fruit of the caper bush can be preserved in the same way and is called a caperberry.

The currant-sized capers from Pantelleria and Salina are among the most delicious I have ever tasted. Brined, then preserved in salt (which needs brushing away and then the capers soaking in water for a few minutes), they are tiny bursts of warm flavour, sour, saline and almost mustardy, but also floral, which makes sense when you consider the flower inside. They are also expensive – too expensive for an ingredient and seasoning to use all the time. I buy larger Italian, Greek or Middle-Eastern salted capers for everyday use in pasta sauces, green and egg sauces, or with fish or meat; and little capers under vinegar for more buttery sauces.

You could use both salt- or vinegar-packed capers for today’s dish, both a seasoning and an ingredient for this southern Italian-style fast food, their mustardy flavour complementing the beef like a dab of mustard, maybe.

Beef with tomatoes and oregano (manzo alla pizzaiola)

The term alla pizzaiola means “pizza-makers style”, which refers to the both the speed and the richly seasoned red sauce.

4 slices lean beef (about 100g each and about 3mm thick)

2 garlic cloves

6 tbsp extra-virgin olive oil

400g cherry tomatoes, chopped

1 pinch red chilli

1 pinch dried oregano or marjoram

1 heaped tbsp capers, rinsed

Salt and black pepper

If you wish, thin and tenderise the beef with a meat basher and make little cuts on the edges to stop them curling. Peel and crush the garlic with the back of a knife so it breaks but remains whole. In a large frying pan, cook the garlic in the olive oil over a medium heat until lightly golden and fragrant, then remove.

Now fry the meat, first on one side, then the other – in two batches if they don’t fit in the pan in a single layer. Set aside on a warm plate.

Add the chopped cherry tomatoes to the meaty juices in the pan and fry for a few minutes, pressing them with the back of a wooden spoon. Add the capers, red chili, oregano or marjoram, a pinch of salt and few grinds of pepper and cook for 10 minutes or so, until rich and saucy.

Return the slices of meat back to the pan, spooning the sauce over the top and cook for a few minutes more. Serve hot with bread, or – as they do at our local trattoria in Sicily – with chips and a glass of red wine.