Cosmo Kramer had an idea on TV's "Seinfeld," for a pizza business "where you make your own pie."Now that idea may not be such pie in the sky.One of the fastest growing restaurant concepts is fresh, fast, build-your-own thin-crust pizzas baked in two minutes inside a flaming oven.Several large established players are grabbing a slice. Buffalo Wild Wings started a joint venture called PizzaRev, which is setting up franchises. The creators of Wetzel's Pretzels created Blaze Pizza, which has opened a half dozen stores so far, with 150 more planned. There's Pie Five, owned by Pizza Inn, and Pieology's chief investor is former tennis star Michael Chang.Even the founders of California Pizza Kitchen, Rick Rosenfield and Larry Flax, have come out of retirement with plans for their own concept later this year. "It's a land grab," said Rosenfield.Perhaps the most talked about concept, though, is one on a deliberately slow growth path. Pizzeria Locale opened in Denver last May, a joint venture between two award-winning fine dining restaurateurs and Chipotle. Lachlan MacKinnon-Patterson and Bobby Stuckey moved from The French Laundry in Napa, Calif., to Boulder, Colo., a decade ago so they could open Frasca Food and Wine. In 2011, they opened the first Pizzeria Locale next door, a full service restaurant. Chipotle co-founder Steve Ells was a fan, according to the owners, and suggested it was something they could work on together.Two years later, the new Pizzeria Locale in Denver opened, looking and feeling very much like a Chipotle: There's an assembly line making customers' pizza. They pick the ingredients, and watch the food being prepared and going into the oven. It's all done in a few minutes."We're going full circle on pizza," said Stuckey. Back over 100 years ago, he said, "Pizza was a healthy way to eat, something that was inexpensive but with great ingredients, in Naples, Italy. Then post-World War II, we created the disaster of pizza. … We're trying to turn that Titanic back around."The two men have no plans to franchise, though they are looking to expand to two more locations in Denver. Their partners at Chipotle apparently don't mind."The nice thing about the relationship is we get to run the restaurant like we want to run it," said MacKinnon-Patterson. "This is our pizzeria. "Both men say Chipotle has brought in better supply chain sourcing, as well as knowledge about real estate and financing."I actually have learned so much great hospitality and service and team-building techniques from Chipotle," said Stuckey, who, like his partner, has won a James Beard award, a high honor in the restaurant industry."Oh, I think they'll do great in pizza," said Rosenfield. "Frankly, I expected Chipotle to get into that business."He and Flax pioneered the concept of fresh, non-traditional pizzas 30 years ago, but CPK was sold to a private equity firm in 2011. Now both men have come out of retirement to build a new pizza chain beginning later this year in Los Angeles. They say it will be different than most of the new concepts."The only thing we can say about it is, it will have a design element that is better, we think, than the ones out there," said Rosenfield."We have a lot more pizzas in us," Flax added. "What we have in mind is to open a place that women are comfortable in, and that's a little different than maybe what people are doing now.""It's definitely an arms race," said Stuckey. His restaurant recently lowered prices after the owners realized the setup was more efficient than they expected. Now pizzas start at $5.75, and sales have improved. "People come in and realize they can afford to come here a few times a week."