Cardoons, swiss chard, eggplants, zucchini, asparagus, and other vegetables, whether cooked alone or as part of a more elaborate presentation, are typically served as a first course in Spain, rather than as an accompaniment to a main course (a main-course accompaniment is usually roasted or fried potatoes, potato puree, or white rice). Since some of these vegetables dishes, such as the mixed-vegetable menestra de verduras from Navarra, require a lengthy preparation - often far longer than grilled meats or fish - it's fitting that they receive special attention at the table.
However, many of these first courses could indeed make wonderful accompaniments in the American sense. For example, in Spain, the classic La Mancha stew, a simple blend of tomatoes and peppers, is often served with fried or scrambled eggs as a first course for lunch or dinner, but it would go well with grilled fish or meat as a side dish, too.
And the versatility of these dishes, despite their prescribed place on the Spanish menu, does not end there. Most of these first courses can be served as main courses by simply increasing the portion size.
Escalivada: Catalonians eat this dish as a first course or as an accompaniment to meats. The special characteristic of these roasted vegetables is their smoky flavor, since orthodoxy demands roasting them over embers (the Catalan word escalivar means 'to roast over ashes or embers'). I have prepared them in the oven with good results.
Zarangollo, a simple dish, which combines the ubiquitous zucchini of Murcia with onions, is a favorite of Murcian cooks, who prepare it both with and without eggs.
Menestra de verduras: Menestra is one of the irreplaceable dishes of Navarra cuisine. Menestra can be served as a side dish to fish or meat, or as a main course in its own.
Sauteed Swiss Chard with Raisins and Pine Nuts: In Catalonia, this is an everyday first course, with spinach sometimes standing in for the Swiss chard. Cooks in the Balearic Islands combine these same ingredients to make the filling for cocarrois, their traditional vegetable turnovers.