Malaga - I love Ensalada de Tomate but how do I make it myself?

Over the past week anytime I've eaten out I've had an Ensalada de Tomate and where ever it's been (Villanueva del Rosario, Villanueva del Trabuco, Mijas, Archidona) it's always been a plate of sliced beef tomatoes covered in (presumably) olive oil, a load of salt & a herb or two.
But for something presumably so simple. I can't find a recipe online, they're all suggesting onions or bell pepper. So I'm asking - what's the herb?