I remember, when I was in the south of Italy, eating eggplant that had been roughly chopped, sprinkled with dried wild oregano, doused with olive oil, and then roasted with a little garlic and a lot of red onions. Indeed, a friend of mine from Campania says this is the way her mother always cooks eggplants, sometimes throwing chopped potatoes into the oven pan at the same time. This, below, is my version: quicker, yes, but I also like the way it can be eaten as an appetizer or part of an antipasti table, and even as an entree course, sprinkled with some ricotta salata (the deliciously salted, semi-dried kind) or crumbled feta, or as an accompaniment to meat and fish. If you are adding cheese, then sprinkle it over before topping with the onions, which are turned a glorious, luminescent puce by their red-wine vinegar marinade (an old and favorite trick of mine).
Slice the baby eggplants in half lengthwise, keeping the stalks on; this is an aesthetic consideration, nothing to do with flavor, but humor me.
Pour the 3 tablespoons regular olive oil into a very shallow roasting pan, sprinkle in the dried oregano, add the eggplants, cut-side down, and swirl them gently around. then turn them so they are cut-side up and put the pan in the hot oven for 15 minutes, by which time they should be tender and turning gold in parts.
As soon as the eggplants are in the oven, put the fine half-moons of red onion in a bowl and cover with the red wine vinegar and salt.
Remove the cooked eggplants to a platter, and now whisk into the vinegary onions the extra-virgin olive oil, then grate in (or mince and add) the garlic and, finally, whisk in the cold water.
Pour this over the warm eggplants, using your hands to arrange the glowingly pink onion over them evenly, then leave it all for about half an hour to cool to room temperature before you eat, scattering with fresh oregano, if you have any, when serving.