There’s debate about whether the bread needs to be toasted. Most Southerners, like Mary, would say no: That soft texture is central to the traditional tomato-sandwich experience. But Jason Skrobar, a food stylist and author of the coming “The Book of Sandwiches,” calls for toasted sourdough in a variation with sun-dried-tomato mayonnaise, which he calls My Perfect Sandwich. My colleague J. Kenji López-Alt, a Seattle resident, pan-toasts just one side of each slice, which he turns inward so the outsides are still soft, a key feature of the classic. (It should be noted that neither Skrobar nor López-Alt is Southern.)

Alternatively, the briefest stint in a toaster means you can have the best of both worlds: The bread keeps its structure under a juicy tomato while maintaining its pillowy softness inside. To each their own. As long as you have to eat your dripping sandwich over the sink, then you’re in the ballpark.

The hallmark of a good tomato sandwich, for me, is mayonnaise that slathers and pools against the tomato. If you’re from the South, “you either grew up in a Duke’s household or a Hellmann’s household,” Mary says. To my mind, the whole Duke’s-versus-Hellmann’s debate couldn’t be more boring or irrelevant (though I enjoy riling people up every year). I use mild-tasting Hellmann’s in this particular case, because I like to sprinkle a little furikake over the mayonnaise before sandwiching the tomatoes. The seaweed in the flavorful rice seasoning amps up the tomato’s savoriness, intensifying the harmony of fruit, carb and condiment. Flavor-forward Duke’s or even Kewpie, delicious though they are, would overpower everything in my perfect tomato sandwich.

All year, I dream of such a sandwich — the first good tomato sandwich of the year.

Recently, Mary told me that she found excellent heirloom tomatoes at the farmers’ market, those delicious ugly ones in red, green and purple. She also restocked her cherished Merita bread, used Duke’s (of course) and filmed herself eating her favorite sandwich for her 400,000 fans. “This is the happiest I’ve ever been,” she said to me, describing how lucky she feels to get to work for herself, to make A.S.M.R. videos that help people all over the world — like me — relax and fall asleep every night. Tonight, as I dream of my tomato sandwich, Mary builds her own, warning us calmly and quietly, “Don’t knock it till you’ve tried it.”