With the opening of a 24-hour downtown brasserie, a Joachim Splichal fish restaurant in the old Maple Drive space, a grand sushi bar in the Eurochow space, a Japanese chain alighting in Century City and a major expansion of R23, this is probably the busiest few days for restaurant openings this year. Yet for some of us, the most exciting food news of the week is the grand premiere of . . . a hot dog cart, parked a few yards up from Beacon, near the entrance to the old Helms Bakery complex. The cart’s proprietor is Sue Moore, a former Chez Panisse forager whose cart outside San Francisco’s AT&T Park has been one of the few compelling reasons to attend Giants games in the last few years. Her hot dogs are made with organic, grass-fed, sustainably raised beef; her bratwurst from organic Berkshire pork; her Italian sausage, should you be lucky enough to run across it, from rare-breed Heritage pigs. And none of this would matter if the hot dogs weren’t great, but they are: taut, delicious natural-skin beauties that snap like rim shots when you bite into them, mildly seasoned, tucked into griddled buns and served, if you want them that way, with grilled onions, organic sauerkraut and an occasional mystery condiment that Moore hides under the counter like the secret stash at a comic-book store. On a recent Sunday, many of the customers appeared to be artists, skinny models and sitcom personalities, thrilled to have found an alternative to Pink’s. Helms Avenue, between Venice and Washington boulevards, Culver City. Open Tues.-Fri. noon-2:30 p.m., Sat.-Sun. noon-4 p.m.