From vegetarian times. Preparation time is a guesstimate. This festive main-course tart celebrates summer by showcasing two special summertime vegetables: fresh corn and vine-ripened tomatoes. When still hot from the oven, the filling is soft and custardy, but firms slightly after cooling. For extra Mexican-style flair, enrich the filling with sliced black olives and sliced scallions, garnish the tart with avocado slices, and pass heated corn or flour tortillas and a side dish of spiced black beans or frijoles refritos. For a South-of-the-Border beverage, try chilled Mexican beer. Select something light such as a meringues or slices seasonal fresh fruit for dessert.